EXPLAIN (why) each of the following trends of atomic properties of main group el

Question

EXPLAIN (why) each of the following trends of atomic properties of main group elements in the Periodic Table. Atomic size decreases from left to right across a period and increases from top to bottom down a group; Ionization energy increases from left to right across a period and decreases from top to bottom down a group; Chemical reactivity for metals decreases from left to right and increases from top to bottom, but the chemical reactivity for nonmetals increases from left to right and decreases from top to bottom.

Explanation / Answer

a) atomic size decreases left to right across a period due to increase in nuclear charge and the incoming electron resides in the same shell.

Atomic size increases down the group due to addition of an extra shell at each successive element in a group from top to bottom.

b) ionisation energy increases across a period from left to right due to increase in nuclear charge. As nuclear charge increases, the valence electrons are firmly attracted by the nucleus so that requires high energy to remove them.

Ionisation energy decreases down a group due to increase in atomic size, the valence electrons are not so firmly held by nuclear attraction force so that requires less energy to remove them.

c) metallic nature means tendency to loose an electron. Metallic nature decreases from left to right due to increase in nuclear charge. Therefore chemical reactivity of metals decreases from left to right.

Non metals reactivity increases from left to right due to increase in nuclear charge and electronegativity.

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