Question

if an element atomic number (z)="A" is an inert gas; in which group would you find an element with atomic number "A-1"(A minus one )?​

Answer 1

Given info : if an element atomic number (z)="A" is an inert gas .

To find : in which group would we find an element with atomic no A - 1.

Solution : modern periodic table is periodic function of atomic number. These elements are characterized by groups and periods.

1st group denotes alkali metals

2nd group denotes alkaline earth metals.

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16th group denotes chalcogens or oxygen family

17th group denotes halogens or Fluorine family.

18th group denotes inert gases

Here you see, halogens come up just before inert gases.

So if A belongs to inert gas family then A - 1 definitely belongs to halogens family.

Therefore in 17th group, we find an element of atomic no A - 1.