Name the most metallic element and most non-metallic element in second period.

Name the element having general electronic configuration ${\mathrm{ns}}^2{\mathrm{np}}^4$ in fourth period.

Consider the ground state electronic Configuration given below.
(A) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^6$
(B) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^4$

Consider the ground state electronic Configuration of some elements given below.

(A) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^6$

(B) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^4$ (C) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^2$

(D) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^1$

(E) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^5$

Arrange the elements based on the above electronic configurations in the ascending order of their electron affinity.

What is the cause of periodicity in the properties of elements? How do the following properties vary in a (a) group, (B) period?

Atomic size

What is the cause of periodicity in the properties of elements? How do the following properties vary in a (a) group, (b) period?

Electronegativity.

What is the cause of periodicity in the properties of elements? How do the following properties vary in a (a) group, (B) period?

Ionization energy

Arrange the given elements. 

$\mathrm{H}, \mathrm{He}, \mathrm{Li}, \mathrm{Be}, \mathrm{B}, \mathrm{C}, \mathrm{N}, \mathrm{O}, \mathrm{F}, \mathrm{Ne}, \mathrm{Na}, \mathrm{K}, \mathrm{Rb}, \mathrm{Cs}.$

In the order of decreasing size in the period.