CBSE 10th Standard Science Subject Periodic Classification of Elements Ncert Exemplar 5 Mark Questions 2021
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CBSE 10th Standard Science Subject Periodic Classification of Elements Ncert Exemplar 5 Mark Questions 2021
10th Standard CBSE
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Reg.No. :
Science
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Which element has :
(a) two shells, both of which are completely filled with electrons?
(b) the electronic configuration 2, 8, 2?
(c) a total of three shells, with four electron in its valence shell?
(d) a total of two shells, with three electrons in its valence shell?
(e) twice as many electrons in its second shell as in its first shell?(a) -
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?(a) -
The position of three elements A, B and C in the Periodic Table are shown below:
Group 16 Group 17 - - - A - - B C (a) State whether A is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller in size than B?
(d) Which type of ion, cation or anion, will be formed by element A?(a) -
In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium?
(a) -
Compare and contrast the arrangement of elements in Mendeleev's Periodic Table and the Modern Periodic Table.
(a)
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CBSE 10th Standard Science Subject Periodic Classification of Elements Ncert Exemplar 5 Mark Questions 2021 Answer Keys
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(a) Neon (Ne), Neon has two completely filled shells with 2 electrons in K shell and 8 electrons in L shell.
(b) Magnesium (Mg).
(c) Silicon (Si). Silicon has a total of three shells. K shell has 2 electrons, L has 8 and M i.e. valence shell has 4 electrons.
(d) Boron (B). It has a two shells, with 3 electrons in its L i.e. valence shell and 2 electrons in K shell
(e) Carbon (C) has electronic configuration of 2 electrons in K shell and 4 electrons in L shell. Clearly, it has twice as many electrons in its second shell as in its first shell. -
(a) The properties of all elements in the boron family
(i) All the elements show valency of 3.
(b) The properties of all the elements in halogen family
(i) All the elements possess seven electrons in the valence shell. -
(a) Group 17 belongs to halogen family and thus, A is non-metal.
(b) C is less reactive than A because the reactivity of non-metal decreases from top to bottom.
(c) Since the size decreaes across a period on moving from left to right, the size of C is smaller than B because B and C belong to the same period.
(d) A forms anion because C is non-metals for anion (negative ion). -
Atomic number of Calcium is 20 and its electronic configuration is 2, 8, 8, 2. To see the resemblance with Calcium, first we have to check the Electronic Configuration of respective elements.
Elements with given Atomic Number Electronic Configuration Element with Atomic Number - 12 2,8,2 Element with Atomic Number - 19 2,8,8,1 Element with Atomic Number - 21 2,8,8,3 Element with Atomic Number - 38 2,8,18,8,2 From above, it is clear, elements with atomic number 12 and 38 has same electronic configuration of valence shell as that of Calcium, and therefore, will have physical and chemical properties resembling calcium.
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Mendeleev's Periodic Table Modern Periodic Table 1. It has 8 groups and 6 periods
It has 18 groups and 7 periods
2. Transition elements are not separated. Transition elements are given separate place 3. The inert gases were not present The inert gases are present in separate
group.4. Lanthanides and Actinides were not present. Lanthanides and Actinides are at the
bottom of the Periodic Table.5. Position of element i.e.,
group number and period number
cannot be predicted.Group number and period number can
bepredicted from its electronic configuration.6. Elements are arranged accordingto the atomic mass. Elements are arranged according to the atomic
number.
