9. Explain the following:
(a) Group 17 elements are strong non-metals, while
group I elements are strong metals.
(b) Metallic character of elements decreases from left
to right in a period while it increases in moving down
a group.
(c) Halogens have a high electron affinity.
(d) The reducing power of an element increases down
in the group while decreases in a period.
(e) Size of atoms progressively becomes smaller when
we move from sodium (Na) to chlorine (CI) in the
third period of the Periodic Table.
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Answers
Answer:
(a) On moving across a period, nuclear pull increases because of the increase in atomic number, and thus, the atomic size decreases. Hence, elements cannot lose electrons easily. Hence, Group 17 elements are strong non-metals, while Group 1 elements are strong metals.
(b) On moving across a period, nuclear pull increases because of the increase in atomic number, and thus, the atomic size decreases. Hence, elements cannot lose electrons easily. Hence, Group 17 elements are strong non-metals, while Group 1 elements are strong metals. Down a group, the atomic size increases and the nuclear charge also increases. The effect of an increased atomic size is greater as compared to the increased nuclear charge. Therefore, metallic nature increases as one moves down a group, i.e. they can lose electrons easily.
(c) The atomic size of halogens is very small. The smaller the atomic size, the greater the electron affinity, because the effective attractive force between the nucleus and the valence electrons is greater in smaller atoms, and so the electrons are held firmly.
(d) The reducing property depends on the ionisation potential and electron affinity of the elements. In a period, from left to right in a horizontal row of the periodic table, the atomic size decreases and the nuclear charge increases, so the electron affinity and ionisation energy both increase. Hence, the tendency to lose electrons decreases across the period from left to right and thus the reducing property also decreases across the period from left to right.
The electron affinity and ionisation potential decreases along the group from top to bottom. Hence, the tendency to lose electrons increases, and thus, the reducing property also increases along the group from top to bottom.
(e) In a period, the size of an atom decreases from left to right. This is because the nuclear charge, i.e. the atomic number increases from left to right in the same period, thereby bringing the outermost shell closer to the nucleus. Therefore, considering the third period given above, it has been found that sodium is the largest in size, while chlorine is the smallest.
Explanation:
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Answer:
1 Solution. On moving across a period, nuclear pull increases because of the increase in atomic number, and thus, the atomic size decreases. Hence, elements cannot lose electrons easily. Hence, Group 17 elements are strong non-metals, while Group 1 elements are strong metals
2 Down the group, the effective nuclear charge experienced by valence electrons decreases because the outermost electrons move further away from the nucleus. ... Hence, metallic character decreases across a period and increases down a group.
3 The atomic size of halogens is very small. The smaller the atomic size , the greater the electron affinity , because the effective attractive force between the nucleus and the valence electrons is greater in smaller atoms , and so the electrons are held firmly.
4 the reducing power of element increases down in the group while decreases in the period. ... Reducing power depends upon the ease of ejection of electron from an atom. As we move down the group, effective nuclear charge decrease, therefore electron can be easily ejected and reducing power increases.
5 Solution. The size of atoms decreases progressively, on moving from sodium (Na) to chlorine (Cl) in the third period because the atomic number of the elements increases. Likewise, the number of electrons and protons in the atoms also increases.