Question

3. An atom of an element has two electrons in the valence shell and two consecutive inner shells have
8 electrons each. Calculate the atomic number of the element.
(1) 19
(2) 20
(3) 30
(4)18​

Answer 1

Answer:

The atomic number of that element will be 20 that is calcium as it is clearly specified in the question that there are 4 energy shells with two inner shells containing 8 electrons each and we also know that the innermost shell can have maximum 2 electrons or 1 electron only.It is also given that it has two valence electrons

This means that there are total 20 electrons.

2 in innermost shell

8 in two inner shells (8×2=16)

2 in outershell

Hence there are 2+16+2=20 electrons in total.

Note:

⭐The innermost shell can have maximum 2 electrons or 1 electron only.

⭐The outermost shell or valence shell can have maximum 8 electrons or less than 8 electrons.

➩Valence Electrons:

The electrons present in the outermost shell of an atom are called Valence electrons.

➩Valence Shell:

The outermost shell of an atom that contains the valence electrons is called Valence shell.

Answer 2

Answer:

option 2 is correct answer