Periods and Electronic Configuration (23)

1. On going through the modern periodic table it is seen that the elements Li, Be, B, C, N, O, F and Ne belong to the period-2. Write down electronic configuration of all of them.

→ The electronic configurations are given below:

Element	Atomic Number (z)	Electronic Configuration
Li	3	2, 1
Be	4	2, 2
B	5	2, 3
C	6	2, 4
N	7	2, 5
O	8	2, 6
F	9	2, 7
Ne	10	2, 8

2. Is the number of valence electrons same for all these elements?

→ No, the number of valence electrons is not the same for all these elements.

3. Is the number of shells the same in these?

→ Yes, the number of shells is same (2), in all these elements.

You will find that the number of valence electrons is different in these elements. However, the number of shells is the same. You will also find that, while going from left to right, within the period, the atomic number increases by one at a time and the number of valence electrons also increases by one at a time.

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