Question

Question #e453d

Answer 1

The arrangement of electrons in the orbitals of an atom or molecule.

Explanation:

So basically the electronic configuration tells us which element is present in which groups, in which periods and in which block (s block, p block, d block and f block).

By knowing how many electrons are present in the shells, we can find the place of an element in the periodic table.

Q: Find the electronic configuration of aluminium?

Ans: `"Al"` has an atomic number equal to `13`

So,

`(1s^2)/"K" " " (2s^2,2p^6)/"L"" "(3s^2,3p^1)/"M"`

Here `"K`" is the first shell, `"L"` is the second, and `"M"` is the third shell (the valence shell).

As `n = 3`, `"Al"` is present in the `"3rd"` period. Since the total number of electrons in the valence sub-shells are

`2+1=3`

it must be present in group lllA (in Roman Numerals). or group 13. and in the last shell, we have a `"p"` so we can say that aluminium is present in the p block.