Question

What is the electronic configuration of an element of mass 31 and atomic number 15?

Answer 1

Answer:

Phosphorous

Mass number = 31

Atomic number = 15

To find:

The electronic configuration and valency.

Solution:

Electronic configuration = ( 2, 8, 18, 32, ... )

Here,

The atomic number = 15

And so,

Electronic configuration = ( 2, 8, 5 )

The third shell can occupy 8 electrons or 18 electrons.

Hence, the element needs 3 more electrons to fill the third shell.

Therefore, valency = 3.