Question

Predict the block, periods and groups to which the following elements belong.

i. Mg (Z = 12) 

ii. V (Z = 23) 

iii. Sb (Z = 51) 

iv. Rn (Z = 86) 

v. Na (Z = 11) 

vi. Cl (Z = 17)

Answer 1

i. Mg (Z = 12): Atomic number of Mg is 12. 

Electronic configuration is 1s² 2s² 2p⁶ 3s².

Block: Since the last electron enters s subshell (3 s), Mg belongs to s-block.

Period: n = 3. Therefore, it is present in the third period.

Group: For s-block element, group number = number of valence electrons = 2. Hence, it belongs to group 2.

ii. V (Z = 23): Atomic number of V is 23.

Electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d³ 4s².

Block: Since the last electron enters d subshell (3d), V belongs to d-block.

Period: n = 4. Therefore, it is present in the fourth period.

Group: For d-block elements, group number = 2 + number of (n – 1)

d electrons = 2 + 3 = 5. 

Hence, it belongs to group 5.

iii. Sb (Z = 51): Atomic number of Sb is 51.

Electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p³.

Block: Since the last electron enters p subshell (5p), Sb belongs to p-block.

Period: n = 5. Therefore, it is present in the fifth period.

Group: For p block elements, group number = 18 – number of electrons required to complete octet = 18 – 3 = 15. 

Hence, it belongs to group 15.

iv. Rn (Z = 86): Atomic number of Rn is 86.

Electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶.

Block: Since the last electron enters p subshell (6p), Rn belongs to p-block.

Period: n = 6. Therefore, it is present in the sixth period.

Group: For p block elements, group number = 18 – number of electrons required to complete octet = 18 – 0 = 18. 

Hence, it belongs to group 18.

v. Na (Z = 11): Atomic number of Na is 11.

Electronic configuration is 1s² 2s² 2p⁶ 3s¹.

Block: Since the last electron enters s subshell (3s), Na belongs to s-block.

Period: n = 3. Therefore, it is present in the third period.

Group: For s-block element, number of the group = number of valence electrons = 1.

Hence, it belongs to group 1.

vi. Cl (Z = 17): Atomic number of Cl is 17.

Electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁵.

Block: Since the last electron enters p subshell (3p), Cl belongs to p-block.

Period: n = 3. Therefore, it is present in the third period.

Group: For p block elements, group number = 18 – number of electrons required to complete octet = 18 – 1 = 17.

Hence, it belongs to group 17.