Question

How do we calculate electronic configuration of an element from its mass number and atomic number

Answer 1

For elements of atomic number more than 20

Take an example of Iron which has atomic number 26

First calculate the electronic configuration of its sub- shells.

Fe(26): 1s2 2s2 2p6 3s2 3p6 4s2 3d6.

Then, calculate the electronic configuration of its shells.

Fe(26): 2 8 14 2.

EXCEPTION: Chromium (Atomic No.-24) and Copper (Atomic No.-29)

Cr(24): 1s2 2s2 2p6 3s2 3p6 4s1 3d5. Cr(24): 2 8 13 1

Cu(29): 1s2 2s2 2p6 3s2 3p6 4s1 3d10. Cu(29): 2 8 18 1.

For the elements whose atomic number is greater than 21, it will be easy if you calculate the electronic configuration of the sub-shells of that element and then calculate the electronic configuration of the shells.

By this way we can find it easily

Hope it helps

Answer 2

Explanation:

The systematic arrangement of electrons in the orbitals is called electronic configuration. The electronic configuration increases in the outermost valence shell which relates to its position in the modern periodic table.

The electronic configuration of element with atomic number 16 is 2,8,6. This indicates that the element belongs to group 16 and period 3 as the number of valence shell is 3.

The valency is calculated as follows:

Firstly, write the electronic configuration of the element.

If the valence electrons are more less than or equal to four then the valency is the number of valence electrons.

If the valence electrons are more than 4 then valency is (8-number of valence electrons).