Question

a) What is the usual number of valence electrons and valency of group 18 elements of the periodic table?
 b) What happens to the number of valence electrons in the atoms of elements as we go down in the group of the periodic table?

Answer 1

Hint : To answer this question, we first need to understand what a periodic table is. The periodic table gets its name from the way the elements are arranged. They're arranged in rows and columns, as you can see. The horizontal rows (from left to right) are referred to as 'periods,' while the vertical columns (from top to bottom) are referred to as 'groups.'

Complete Step By Step Answer:
Valence electron- A valence electron is an outer shell electron associated with an atom that can participate in the formation of a chemical bond if the outer shell is not closed; in a single covalent bond, both atoms contribute one valence electron to form a shared pair in chemistry and physics.
Valency- The combining power of an element is known as valency. The valency of elements in the same group of the periodic table is the same. The number of electrons in an element's outer shell determines its valency.
Group 18 elements –
Members of group 18 in the modern periodic table are known as the noble gases.
-Helium (He)
-Neon (Ne)
-Argon (Ar)
-Krypton (Kr)
-Xenon (Xe)
-Radon (Rn)
The group's members have eight electrons in their outermost orbit (except helium which has two electrons). As a result, they have a stable setup. Group 18 elements are gases with a low chemical reactivity, meaning they don't form many compounds. As a result, the elements are referred to as inert gases. Noble gas elements, like the other group elements, show trends in their physical and chemical properties. The following sections go over the general characteristics of noble gases.
So the final answer are -
Because group 18 lacks a valence electron, its valency is zero, indicating that it is stable.
The valency of all elements in that group remains constant as we go down the group, i.e. the valency of the entire group remains constant, but the number of shells increases.

Note :
Noble metals are metallic elements that, even at high temperatures, show exceptional resistance to chemical attack. The noble metals correspond to the noble gases in the periodic table. Copper (Cu), rhenium (Re), and mercury (Hg) are all noble metals, according to more comprehensive lists.