Question

The atomic number of elements is 17. The valency of the element is ________.
(A) 3
(B) 4
(C) 1
(D) 2

Answer 1

The atomic number or proton number of a chemical element is the number of protons found in the nucleus of every atom of that element. The atomic number uniquely identifies a chemical element. It is identical to the charge number of the nucleus.

Complete step by step answer:
We have been provided with an element with atomic number is 17,
We need to find the valency of the element,
Valency is the combining power of an element. Elements in the same group of the periodic table have the same valency. The valency of an element is related to how many electrons are in the outer shell.
We have been given an element with atomic number is 17,
So, the electronic configuration would be: 2,8,7
Therefore, it requires one more electron to become stable,
So, as it requires to gain an electron to complete its octet it is probably a non-metal,
Non-metals are natural materials that do not produce heat or electricity and that are structurally brittle (cannot be easily rolled, moulding, extruding or pressing). Chemically hydrogen, carbon, nitrogen, oxygen, phosphorus, arsenic, and selenium are the non-metallic elements in the periodic table.

It belongs to 3rd period and it has a smaller size as compare to other members of the serial because size of atom decreases in a period due to increase in the nuclear charge,
Therefore, the valency would be: 1.
So, the correct answer is “Option C”.

Note: Some key characteristics of a valence electron are; For the main group elements, the valence electron exists only in the outermost electron shell. A valence electron can exist in the inner shell of a transition metal. An atom consisting of a closed shell of valence electrons will usually be chemically inert.