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10th Kendriya Vidyalaya Periodic Test -3 original papers 2019 
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For more : see post 10th Biology: HEREDITY AND EVOLUTION SOLVE  1. “Different species use different strategies to determine sex of a new born individual. It can be environmental cues or genetically determined‟. Explain the statement by giving example for each strategy. Ans: Environmental Cue – (a) In some animals, the temperature at which fertilized eggs are kept determines whether the developing animal in egg is male or female eg lizard (b) In some animals like snail, individual can change sex. Genetically – A child who inherits an x chromosome from her father will be a girl and one who inherits a y chromosome from the father will be a boy. 2. a. Define the term Gene. b. The gene for red hair is recessive to the gene for black hair. What will be the hair colour of a child if he inherits a gene for red colour from his mother and a gene for black hair from his father? Express with the help of flow chart. Ans: a. The functional unit of DNA which are made of nucleic acids and protein is called gene. b. Given Black hair – father Dominant [ BB ] and Red hair – Mother – Recessive [ bb] Parents Father BB/Bb X Mother Bb/bb F1 Bb (Black) 3 .a. Mention any two point of difference between acquired and inherited traits. b. If the tail of a mouse is cut for twenty one generations, will the tail occur in the twenty second generation of that mouse? Give reason to support your answer. c. Define the term – Natural Selection. Ans: a. Acquired Traits Inherited Traits Trait acquired during its lifetime Traits inherited from its parents cannot passed on to progeny passed on to progeny Not present in the genetic makeup Present in the genetic makeup b. The mouse continue to have information for presence of tail in its DNA So, mouse will continue to have tail, because it is an acquired trait. c. The process by which nature selects organisms which are more suitably adapted and possesses favourable variations is called Natural Selection 4. With regard to turnip, carrot, sweet potato and potato, three belong to the same category. Identify those three modifications and mention whether they are homologous or analogous. Also mention the reason why the fourth modifications do not belong to the same category. Ans: Turnip, Carrot, Sweet Potato – are modified root – Homologous organs but Potato – modified stem. 5. What are chromosomes ? Explain how in sexually reproducing organisms the number of chromosomes in the progeny is maintained Ans: Chromosomes are thread like structures made up of DNA found in the nucleus of cell. The original number of chromosomes becomes half during formation of gamete. Hence, when the gametes combine, the original number of chromosomes gets restored in the progeny. 6. Explain with an example for each, how the following provides evidences in favor of evolution in organisms: (a) Homologous organs (b) Analogous organs (c) Fossils Ans: Homologous organs – Study of homologous organs suggests that the organs having same structure but performing different functions have evolved from a common ancestor. Ex. - forelimbs of a frog, lizard, bird and man. Analogous organs – Study of Analogous organs suggests that these organs are having different origin and structural plan but perform same function . These are evolved from different ancestors and show adoption of organs for common use. Ex. – wings of butterfly and wings of bat. Fossils – provide the missing links between two species. Fossil Archaeopteryx possess features of reptiles as well as birds. This suggests that birds have evolved from reptiles 7. Explain the following: (a) Speciation (b) Natural Selection Ans: Speciation – The process by which new species develop from the existing species is known as speciation. Speciation takes place when variation is combined with geographical isolation. Natural selection – this is the change in frequency of some genes in a population. This give survival advantage to a species from elimination. Ex. – in a population of beetles, a new variation (green colour) get survival benefit / advantage to green beetles whereas other (red) perishes. 8. How do Mendel’s experiments show that the (a) traits may be dominant or recessive, (b) traits are inherited independently ? Ans: a) When Mendel cross pollinated pure tall pea plants with pure dwarf pea plants, only tall plants were obtained in F1 generation. On self pollinating the F1 progeny, both tall and dwarf plants appeared in F2 generation in the ratio 3:1 Appearance of tall character in both the F1 and F2 shows that it is a dominant character. The absence of dwarf character in F1 generation and its reappearance in F2 shows dwarfness is the recessive character. b) When Mendel conducted a dihybrid cross having two sets of characters, he obtained only one set of parental characters in F1 generation whereas in F2 generation he obtained both the set of parental characters now recombined in the ratio of 9:3:3:1. The appearance of new recombinants in the F2 generation along with parental type shows that traits are inherited independently. 9. What do you mean by Gene flow, Genetic drift . Ans: Gene flow is transfer of gene between population that are partly but not completely separated. Genetic drift: It is the random change in the frequency of alleles (gene pair) in a population over successive generations. Genetic drift takes place due to (a) Severe changes in the DNA (b) Change in number of chromosomes 10. ‘‘It is possible that a trait is inherited but may not be expressed.’’ Give a suitable example to justify this statement. Ans: Yes, it is possible. Example – When pure tall pea plants are crossed with pure dwarf pea plants, only tall pea plants are obtained in F1 generation. On selfing tall plants of F1, both tall and dwarf plants are obtained in F2 generation in the ratio 3:1. Reappearance of the dwarf character, a recessive trait in F2 generation shows that the dwarf trait/ character was present in individuals of F1 but it did not express (due to the present of tallness, a dominant trait / character). 11. ‘‘It is a matter of chance whether a couple will have a male or a female child.’’ Justify this statement by drawing a flow chart. Ans: A human male has XY sex-chromosomes and produces two types of sperms (heterogametic). Either with X-chromosome or with Y-chromosome. A human female has XX sex-chromosomes and produce ova of one type (homogametic) all with X-chromosomes. Parents Male Female Gametes X Y XX Progeny XX XY Female (50%) Male (50%) 12. What is speciation? List four factors that could lead to speciation. Which of these cannot be a major factor in the speciation of a self-pollinating plant species? Explain. Ans: Speciation is the process of the formation of new species from pre-existing ones. Factors – (i) Mutations (ii) Natural selection (iii) Genetic drift (iv) Geographical Isolation Geographical isolation cannot be a major factor in the speciation of a self pollinating plant species. This is because physical barrier cannot be created in self pollinating plants. 13. (a) Cite the evidence on the basis of which it is concluded that birds have evolved from reptiles. (b) Insects, Octopus, Planaria and Vertebrates also possess eyes. Can these animals be grouped together on the basis of the eyes they possess. Why or why not ? Give reason to justify your answer. Ans: a) i) Fossils showing imprints of feathers along with the bones in dinosaurs / reptiles found, ii) They could not fly and presumably using the feathers for insulation, iii) Later they developed / evolved and adapted feathers for flight. iv) Thus, they give evidence that birds have evolved from reptiles. b) No, the structure of the eye in each of these organisms is different / they have separate evolutionary origins. 14. How does sexual reproduction leads to similarities as well as variations ? Ans: Similarities and variations are dependent on the type of allele combination an offspring will get from their parents. If a child get dominant alleles from father then he will look quite similar to his father and quit different from his mother. If he got a combination of dominant alleles from both the parents then he will be quite different from both the parents. 15. What is hybrid? Give term for (i) externally exhibited traits (ii) Traits developed by gene - Ans: Organism having two or more mixed traits are called hybrid . Plants having two pairs of contrasting characters is called dihybrid. (i) Externally exhibited traits : Phenotype (ii) Traits developed by gene – Genotype Visit page dedicated Board exam Heredity and evolution  10th Light Numerical Question Test Paper-1 Download File 10th Light Numerical Question Test Paper-2 Download File 10th Light Numerical Question Test Paper-3 Download File 10th Light Numerical Question Test Paper-4 Download File For more study material for Chapter Light Refraction-Reflection-eye
1. What is the function of ozone in upper atmosphere? Ans: It shields the surface of the earth from ultraviolet rays from the Sun. 2. What is meant by “sustainable management”? Why reuse considered better than recycling? Ans: A type of management which encourages utilization of resources that meet current basic human needs while preserving the resources for the needs of future generations. Reuse considered better than recycling as it does not consume energy. 3. Why are forest considered “biodiversity hot spot”? List two ways in which an individual can contribute effectively to the management of forest and wildlife? Ans: In forest large number of life forms such as bacteria, insects, birds, reptiles, mammals, etc are found . it is a region with large biodiversity of endangered species, many of them being highly endemic and such regions being subjected to large scale destruction are designated as “Hot spots” by ecologists. Two ways in which an individual can contribute effectively to the management of forest and wildlife – i) Not allowing cutting of trees ii) To promote / make people aware about the importance of forests and wild life. iii) Not using wild life products / fur coat or any other named product 4. Why do we need to manage our resources carefully ? Ans: These are not unlimited and with a tremendous increase in human population, the demand for resources is increasing at an exponential rate. 5. Why management of natural resources require a long term preservative? Ans: Long term perspective required to meet the needs of the present as well as for the generations to come. 6. List four measure to conserve forest ? Ans: Four measures to conserve forest are: (i) Reforestation of the deforested areas as soon as possible. (ii) Ban on the indiscriminate cutting of trees. (iii) Felling of trees for fuel wood should be avoided. (iv) Overgrazing in forests should be discouraged. 7. Why should biodegradable and non biodegradable waste be discarded in two separate dustbins? Ans: So that the time and energy required in segregation may be saved and waste may be disposed off quickly 8. List two advantages associated with water harvesting at the community level. Ans: Two advantages associated with water harvesting at the community level are : (i) Recharges ground water (ii) Mitigates floods and droughts (iii) Brings rivers and wells back to life and makes more water available 9. Every one of us can do something to reduce our personal consumption of various natural resources. List four such activity based on 3 – R approach. Ans: Four activities every one of us can do to reduce our personal consumption of various natural resources: i) Reduce excessive use of natural resources like water, fossil fuels, etc.. ii) Reuse of some resources instead of wasting (throwing) them, like empty bottles. iii) Recycle the materials like paper to reduce the pressure on existing natural resources. iv) Changes in lifestyle, personal attitudes and practices. 10. The following organisms form a food chain. Which of these will have the highest concentration of non-biodegradable chemicals ? Name the phenomenon associated with it. Insects, Hawk, Grass, Snake, Frog. Ans: Hawk ; Biomagnification 11. What is meant by three types of ‘R’ (3-R’s) to save the environment ? Ans: Reduce, Reuse, Recycle 12.Explain with examples how would you follow the 3-R’s in your school to save the environment. Ans: To save the environment we at school: - Switch off the fans and bulbs when not in use, - Reuse of paper, polythene bags, etc., - Reduce the wastage of water / paper or any other item 13. List four advantages of water stored in the ground as ‘‘ground water’’ Ans: Advantages of water stored in the ground as ‘‘ground water’’ – I. It does not evaporate. II. Spreads out to recharge wells. III. Provides moisture for vegetation over a large area. IV. Does not provide breeding ground for mosquitoes. V. Remain protected from contamination from human excreta, etc.. 14.. Write the full name of the group of compounds mainly responsible for the depletion of ozone layer. Ans: Chloroflurocarbons 15. List two problems that may arise by planting trees of single variety over vast tracts of a forest. Ans: 1. Loss of biodiversity 2. Varied needs of the local people can no longer be met. 3. Degradation of soil 16. Building of big dams gives rise to some problems. List three main problems that may arise. Suggest a solution to any one of these problems. Ans: 1. Social problems 2. Economic problems 3. Environmental problems Solution: Adequate rehabilitation / compensation to the displaced persons / aforestation 17. List two examples of natural ecosystem. Ans: Forests ,Ponds,Lakes 18. Write two advantages of sustainable management of natural resources. Out of the two – reuse and recycle – which is better and why ? Ans: Two advantages - (i) Provides the resources for the present generation. (ii) Preserve the resources for the future generation as well. Reuse is better than recycling because it does not involve use of energy 19. ‘‘Energy flow in food chains is always unidirectional.’’ Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body. Ans: In a food chain the energy moves progressively through the various trophic levels and is no longer available to the organisms of the previous trophic level / energy captured by the autotrophs does not revert back to the solar input. Pesticides used for crop protection when washed away into the soil or water bodies absorbed by plants. On consumption they enter our food chain and being non – biodegradable these chemicals get accumulated progressively and enter our body. 20. What will be the amount of energy available to the organisms of the 2nd trophic level of a food chain, if the energy available at the first trophic level is 10,000 joules ? Ans: 1000 J 21. List two main causes of the pollution of water of the river Ganga. State how pollution and contamination of river water prove harmful for the health of the people of neighbouring areas. Ans: Causes: Disposal of industrial effluents. Human activities like bathing, washing, immersion of ashes, etc. Disposal of untreated sewage Harmful effects on health – Spreads water borne diseases,- Consumptions of contaminated fishes 22. What is biodiversity ? What will happen if biodiversity of an area is not preserved ? Mention one effect of it. Ans: Biodiversity - number and range of variety of species of life forms in an area Effect – loss of diversity may lead to a loss of ecological stability 23. Differentiate between biodegradable and non-biodegradable substances with the help of one example each. List two changes in habit that people must adopt to dispose non-biodegradable waste, for saving the environment. Ans: Biodegradable substances – can be broken down into simpler substances by nature / decomposers/ bacteria/ saprophytes/ saprobionts. Ex. – Human Excreta/ Vegetable peels, etc. Non-biodegradable substances – can’t be broken down into simpler substances by nature / decomposers. Ex. – Plastic/ glass (or any other) (any one) Habits: - Use of separate dustbins for biodegradable and non biodegradable waste, - Reuse of things such as poly-bags, etc., - Recycle of waste - Use of cotton /jute bags for carrying vegetables 24. What is ozone ? How and where is it formed in the atmosphere ? Explain how does it affect an ecosystem. Ans: Ozone (O3) is a molecule formed by three atoms of oxygen. Ozone is formed at at the higher levels of the atmosphere by action of UV radiation on oxygen (O2) molecule. The higher energy UV radiations split apart some moleculer oxygen (O2) into free oxygen (O) atoms. These atoms then combine with the molecular oxygen to form ozone as shown-- O2 ⎯⎯UV⎯→ O + O then, O + O2 ⎯⎯⎯→ O3 (Ozone) Ozone shields the surface of the earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms, for example, it is known to cause skin cancer in human beings. 25. Construct an aquatic food chain showing four trophic levels. Ans: Hydrilla →Scorpio→ Fish → Crane 
1. Gist of Lesson for Quick Revision (By JSUNIL) 2. In 1789, Lavoisier first attempted to classify the elements into two divisions namely Metals and Non-metals. 3. Mendeleev predicted the properties of those missing elements from the known properties of the other elements in the same group. On the basis of this, he named Gallium as Eka-Almunium, Germanium as Eka-Silicon and Scandium as Eka-Boron. 4. Mendeleev's periodic table helped in correcting the atomic masses of some of the elements, based on their positions in the periodic table. For example, atomic mass of beryllium was corrected from 13.5 to 9.0. Atomic masses of indium, gold and platinum were also corrected. 5. In certain pairs of elements like, Ar (40) and K (39); Co (58.9) and Ni (58.6); Te (127.6) and I (126.9) the arrangement was not justified. For example, argon was placed before potassium whereas its atomic mass is more than potassium. 6. The position of hydrogen was not correctly defined. It was placed in Group I although its properties resembled both the Group I elements (the alkali metals) and the group VII elements (the halogens). 7. Lithium, Sodium, Potassium are called Alkalies metal as they react with metal and form alkalies (Caustic solution) 8. Calcium, Strontium, Bromine are called Alkalies Earth metal as they react with metal and form salt as their oxide are alkalies in nature and exist in the Earth 9. Chlorine, Bromine, Iodine are called Halogen as their oxide are alkalies in nature and exist in the Earth 10. Alkali metal and coinage metals (Cu, Ag and Au) which differ widely in properties are placed into the same group. In 1913, an English physicist MOSELEY, as a result of his work on characteristics X-rays of elements discovered a fundamental and most accurate relation between chemical properties and atomic number of elements, known as "Modern periodic law". ACCORDING TO THE MODERN PERIODIC LAW: 1. The chemical and physical properties of elements are the periodic function of their atomic numbers". 2. The properties of elements depend upon their electronic configuration which varies with increasing atomic number in a periodic way". Period: 1. Atomic size decreases in a period. 2-Nuclear charge increases in a period. 3-Ionization potential increases in a period. 4-Electronegativity increases in a period. 5-Electropositivity and metallic character decreases in period. 6-Each period starts with Alkali metal and ends on a Noble gas. For example: 2nd period : Li .................................. Ne 3rd period : Na ..................................Ar 7-First element of each period is most reactive (electropositive), and last element is chemically inert. Group: 1-Group number of an element shows the number of electrons in the outermost shell of that element 2-Atomic size increases in group. 3-Ionization potential of elements decreases down the group. 4-Electronegativity decreases down the group. 5-Metallic character increases down the groups. On the basis of valence shell electronic configuration, periodic table is divided into four distinct blocks of elements. S-block elements All the elements in which last electron enters "ns" orbital are known as s-block elements. Elements of group I-A and II-A belong to s-block. Their valence shell electronic is ns1 to ns2. All the elements of s-block are very reactive and electropositive in nature. S-block elements are good reducing agents. They form ionic compounds. They are all metals and solid. They are low density metals. For example : Li (z=3) 1s2, 2s1 Na (z=11) 1s2, 2s2, 2p6, 3s1 Be (z=4) 1s2, 2s2 p-block elements The elements in which valence electrons enter p-orbital and this orbital is progressively filled are called p-block elements. Their valence shell electronic configuration is from ns2, np1 to ns2, np6. P-block consists of the elements of group III-A to VIII-A (zero-group). They include metals, nonmetals and metalloids. There are 30 elements in six sub-groups of p-block. d-block elements The elements in which last electron enters (n-1) d-orbital are called d-block elements or outer transition elements. Valence shell electronic configuration of these elements is ns2, (n-1) d1-10. All these elements are metals.There are four series of outer transition elements. Fourth series is incomplete. f-block elements The elements in which last electron enters (n-2) f-orbital are called f-block elements or inner transition elements. Their outer electronic configuration is ns2,(n-1)d1,(n-2) f1-14 f-block elements constitute 2 series of elements. (1) lanthanides (2) Actinides Visit fore full study: CBSE Class 10th Periodic Classification   <B = <B’ and <1 = <2
D ABP ~ A’B’P [ AA - similarity] AB/A’B’ = BP/B’P ho /hi = -u/v hi /ho = -v/u Magnification = m = hi /ho = -v/u Derivation or Proof-of-Mirror formula(X) physics Class 10 CHAPTER HOW DO ORGANISMS REPRODUCE SOLVED QUESTIONS
Click here and Visit to Download File 10th CHAPTER HEREDITY AND EVOLUTION-SOLVED QUESTION SOLVED ) Click here and Visit to Download File  HOTS: (High Order Thinking Skill) Questions with Answers:
Q.1. Why is variation beneficial to the species but not necessary for the individual? Ans- Variation is beneficial to the species as it enables a species for its survival. A favourable variation makes an organism to live better in a changed environment and an unfavourable variation will not. So it is not necessarily true that a variation is beneficial to the individual always. Q.2. What is the advantage of reproduction through spores in the case of Rhizopus? Ans: The spores are covered by thick walls that protect them until they come into contact with another moist surface and can begin to grow. Q.3. The simple animals such as planaria can be cut into number of pieces and each piece grows into a complex organism. What is this process known as? Ans: Regeneration Q.4) Name the unicellular organism which caused the disease known as kala-azar. Ans : Leishmania Q.5) Which process taking place in the nucleus of a cell leads to variation in the offspring during reproduction? Ans : DNA copying Q.6. What causes joining up of stock and scion in grafting technique of vegetative propagation in plants? Define the terms stock and scion. Name one positive trait each of the plant contributing scion and stock should have. Ans : The stock and scion unite due to cambial cavity. Stock is the portion on which grafting is done and it provides the roots. Scion is the portion of the plant which is grafted on the other plant and it contributes the stem. The plant contributing scion should have large sized fruits and the plant contributing stock should have deep root system. Q.7 . Which type of layering is done in Jasmine? Ans : Air Layering (Gootee) Q.8 . Where does fertilization takes place in human female? Ans : Oviduct (fallopian tube) Q.9 . Why is it said that “sexual reproduction promotes diversity of characters in the offsprings”? Ans : It is because sexual reproduction results from the fusion of two gametes coming from two different and sexually distinct individuals. This leads to variation, is necessary for evolution. Q.10. What happens if the fallopian tubes are partially blocked and the ovulated eggs are prevented from reaching the uterus? Ans : Fertilization may take place but the zygote may develop in the tube instead of uterus. Q.11 . Name the causative organism of syphilis and gonorrhoea. Ans : Treponema pallidum and Nisseria gonorrhoeae. Q.12 . Why are variation possible in progeny of sexually reproductive individuals? Ans-Variations are possible in progeny of sexually reproductive individuals because copy of DNA in newly formed cell is not identical to copy DNA of original cell. 10th NCERT Solution Intex and Exercise Questions 10th CBSE NCERT Question(1 mark) Solved 10th CBSE NCERT Question( 2 marks) Solved 10th CBSE NCERT Question( 3 marks) Solved 10th CBSE NCERT Test Paper (Solved) Click to download these files Q.What is refraction of light? What are the laws of refraction? Ans: Deviation of ray of light from its original path when it travels from one transparent homogeneous medium to another transparent homogenous medium is called the refraction of light. There are two laws of refraction :- (I ) incident ray, reflected ray and normal lie in the same plane. (ii) The ratio of sine of angle of incidence and sine of angle of refraction is constant i.e. Sin i / Sin r = n. This is also called as Snell’s law. Q. Define Refractive Index: Ans: It is the ratio of speed of light in vacuum to the speed of light in medium is called Refractive index. Q. Give the ratio of velocities of two light waves travelling is vacuum and having wave lengths 4000A0 and 8000A0. Ans: In Vacuum, light of all the wave lengths travel with the same velocity i.e. 3 X 108 m/sec. Q.. For what angle of incidence, the lateral shift produced by parallel sided glass plate is zero? Ans: For <i = 0. Q. What are the factors on which the lateral shift depends? Ans: Thickness of the refracting medium, angle of incidence and its refractive index Q. What is the value of Relative refractive index of air? Ans: One. Q. If speed of light in vacuum = 3 x 108 m/sec and Refractive index of water = 4/3, What is the speed of light in water? Ans: Refractive index of water = Speed of light in vacuum / Speed of light in water; 4/3 = (3 x 108 m/sec )/ (Speed of light in water) Speed of light in water = (3 x 108 m/sec) x ¾ = 9/4 x 108m/sec = 2.25 x 108 m/sec. Q. For the same angle of incidence in media P, Q and R, the angles of refraction are 350, 250, 150 respectively. In which medium will the velocity of light be minimum? Ans: According Snell’s law n = Sin i / Sin = C / V For given angle of incidence (i), V will be minimum, when angle of refraction <r is minimum In given data it is for medium R. Q. A coin in a glass beaker appears to rise as the beaker is slowly filled with water. Why? Ans: It happens on account of refraction of light. A ray of light starting from the coin goes from water to air and bends away from normal. Therefore, bottom of the beaker on which the coin lies appears to be raised.
Q. State Modern Periodic Law. Name the two elements of first period. Q.Two element X, Y and Z belong to 17th group but to 2nd,3rd and 4th period respectively. Number of valence electrons in Y is 7. Find the number of valence electrons in X and Z. Q. How does the metallic character of the elements vary (i) in a group (ii) in a period of the modern periodic table ? Q. Na, Mg, Al and P belong to 3rd period but are placed in first, second, thirteenth and fifteenth group. Number of shells occupied in Mg is three. What is the number of occupied shells in Na, Al and P. Give reason for your answer. Q. What is the number of elements in first , second and third period of the periodic table? Give reason for your answer. Q. Arrange the following elements in the descending order of atomic size and give a reason for your answer. Mg, Cl, P, Ar (Atomic numbers of the above elements are 12, 17, 15, 18 respectively. Q. Mention any two trends exhibited by elements when we go from left to right across the period of periodic table. Q. Given below are the atomic radii of some elements of second period.
Arrange these elements in the increasing order of their atomic number . Give reason for your answer. Q. “Elements in Periodic Table show periodicity of properties” List any four such properties. Q. (a) Atomic number of Mg and Al are 12 and 13 respectively. Write their electronic configuration. (b) Mention the period of the Modern Periodic Table to which the above two elements belong. Give reason for your answer Q. (a) State the Modern periodic law. (b) What is the total number of periods and groups in Modern Periodic Table Q. From the part of a periodic table, answer the following questions
(a) Atomic number of oxygen is 8. What would be the atomic number of, Fluorine ? (b) Out of ‘X’ and ‘Q’ which element has larger atomic size. Give reason for your answer Fluorine. (c) Out of ‘Y’ and ‘Z’ which element has smaller atomic size. Give reason for your answer. Q. (a) Atomic radius of hydrogen is 37pm. Express it in meters. (b) How does atomic size vary in a group and in a period ? Q. (a) What are metalloids ? Write any two examples. (b) Given below are some of the elements of first group Li, Na, K (Their atomic numbers are 3,11,19 respectively and they belong to 2nd 3rd and 4th period respectively) Arrange these in the decreasing order of metallic character exhibited by them. Q. Nitrogen (atomic number 7) and phosphorous (atomic number 15) belong to group 15 of the Periodic Table write the electronic configuration of these two elements. Which of these will be more electronegative and why ? Q. (a) State modern Periodic Law. (b) What are groups and periods in periodic Table? Q. (a) “Silicon is classified as a metalloid.” Justify this classification. (b) Name two more such metalloids. (c) In which part of the Periodic Table we can look for metalloids. On which side of these we can get non- metals ? Q. The following table shows the positions of six elements A, B, C,D,E and F in the modern periodic table
(a) Which element will form only covalent compounds ? (b) Which element is a metal with valency two ? (c) Out of D and E , which one has a bigger atomic radius ? Give reason for your answers. Q. State the modern periodic law. How many groups and periods are there in the modern periodic table Q. Out of the two elements X and Y which has bigger atomic radius ? Give reason to justify your answer. (i) X has atomic number 18 and atomic mass 40 (ii) Y has atomic number 20 and atomic mass 40 Q. Given below is a part of the periodic table.
(a) What happens to the atomic size? Justify your answer. (b) what happens to the metallic character of the elements ? (b) (i) Take about 3mL of Ethanol in a test tube and warm it gently in a water bath. (ii) Add a 5% solution of alkaline potassium permanganate drop by drop to the solution. (iii) What happens to the colour of KMnO4 added initially and then in excess? Give reason. Name the product of this reaction. Q. (a) How does the tendency to gain electrons change as we go down a group ? Give reason. (b) Given below is a part of the periodic table. How does the valency vary, as we move vertically downward from Li to Fr. Give reason?
Q. The electronic configuration of three elements X, Y and Z are given below.
(i) Which element belongs to the second period ? (ii) Which element belongs to the eighteenth period ? (iii) Which element belongs to the second group? (iv) What is the valency of Y ? (v) Y and Z, are they metal or a non – metal ? Q. (a) Element „Y‟ with atomic number 3 combines with element „A‟ with atomic number 17, what would be the formula of the compound ? (b) What is electronic configuration of element with atomic number 10 ? What will be its valency ?
Chapter : 05 : Periodic Classification of Elements [Main Page]
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