The element with atomic number $14$ is hard and forms acidic oxide and a covalent halide. To which of the following categories does the element belong?

Name the element which has:
$(a)$ the electronic configuration $2, 8, 1$.
$(b)$ a total of two shells,with $4$ electrons in the valence shell.
$(c)$ a total of three shells,with $3$ electrons in the valence shell.
$(d)$ one shell which is completely filled with electrons.
$(e)$ twice as many electrons in the second shell as in the first shell.

The scientist who showed that the atomic number of an element is a more fundamental property than its atomic mass is:

Atomic numbers of a few elements are given below: $10, 20, 7, 14$.
$(a)$ What would be the electronic configuration for each of these elements?
$(b)$ Determine the valency of these elements.

$Lithium$,$sodium$,and $potassium$ are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?

Which element has
$(a)$ a total of three shells,with four electrons in its valence shell?
$(b)$ a total of two shells,with three electrons in its valence shell?
$(c)$ twice as many electrons in its second shell as in its first shell?