Question

How do the following change on moving from left to right in a period of the periodic table?

Give examples in support of your answer.

(a) atomic structure (electron arrangements)

(b) Chemical reactivity of elements.

(c) Nature of oxides of the elements.

Answer 1

(a) The number of valence electrons increases by one as we move across any given period.

Therefore as we move from Lithium to Neon in period 2, the valence electrons will increase from 1 to 7.

(b) The metallic character decreases as we move from left to right while the non metallic character increases.

Ongoing from left to right in a period, the chemical reactivity of elements first decreases and then increases.

For example in period 3, Sodium is the most reactive metal and Chlorine is the most reactive non-metal and Silicon is least reactive

(c) The oxides of metals are basic and that of non-metals are acidic in general. Therefore since metallic strength decreases and non-metallic strength increases on moving from left to right across a period, the strength of basic oxides decreases, while the strength of acidic oxides increases.

For example, sodium forms a basic oxide, while sulphur and phosphorus form acidic oxides.