Name the elements in correct order of their increasing atomic numbers present in the first, second and third short periods of the periodic table. State each elements electronic configuration.

Elements of first, second and third period in increasing order of their atomic number are mentioned below (atomic number of each element is mentioned in brackets):

First period — H(1), He (2)

Second period — Li (3), Be (4), B (5), C (6), N (7), O (8), F (9), Ne (10)

Third period — Na (11), Mg (12), Al (13), Si (14), P (15), S (16), Cl (17), Ar (18)

Electronic configuration of the above mentioned elements is as follows —

H — 1

He — 2

Li — 2, 1

Be — 2, 2

B — 2, 3

C — 2, 4

N — 2, 5

O — 2, 6

F — 2, 7

Ne — 2, 8

Na — 2, 8, 1

Mg — 2, 8, 2

Al — 2, 8, 3

Si — 2, 8, 4

P — 2. 8, 5

S — 2, 8, 6

Cl — 2, 8, 7

Ar — 2, 8, 8