Periodic Classification of Elements Test - 2

Sodium and potassium both are alkali metals. Thus, they have the same valency.

Some elements, like the transition metals, have electronic configurations in which electrons from their inner shells can also be used as valence electrons; these elements can have several different oxidation states. Chromium can have a valency of +2, +3 or +6.

Element X₁₀ has complete octet as its electronic configuration is 2, 8.

Among the given configurations, 2, 8, 8, 2 would be the configuration of a metal as this element will show a positive oxidation state by losing two valence electrons.
Z = 2 + 8 + 8 + 2 = 20

The element is calcium.

In modern periodic table, there are 18 columns and 7 periods.

Xenon is the most electropositive among all the noble gases.

Aluminium ion has the largest size than all the other given ions.

Among the representative elements, the atomic radius decreases on moving across the period, due to the increase in the effective nuclear charge.

However, in the transition elements, the electrons are added to the n-1 shell and they screen the valence electrons from the nuclear pull. Therefore, the decrease in the radius on moving left to right across the period is rather slow. Moreover, as after the group 6, the pairing of the electrons in the orbitals leads to repulsions and counters the effect of the increase in the effective nuclear charge.

As a result, the radius of the transition elements remains more or less comparable across the period. Hence, Fe, Co, Ni and Cu have almost similar values of atomic radii.

The ionisation energy of sulphur is less than that of phosphorus because phosphorus has half-filled electronic configuration.

The size of anion is always greater than the corresponding atom.