S Block Elements
Q7 In what ways lithium shows similarity towards Magnesium?
Ans. Lithium resembles magnesium mainly due to the similarity in size of their atoms (Li = 152 pm, Mg = 160 pm) and ions (Li+ = 76 pm, Mg2+ = 72pm).
The main points of similarity:
i. Both have almost similar electronegativities (Li=0.98 and Mg = 1.2)
ii. Both Li and Mg are quite hard. They are harder and lighter than other elements in their respective groups.
iii. Both LiOH and Mg(OH)2 are weak bases.
iv. Both form ionic nitrides when heated in an atmosphere of nitrogen
6Li + N2 → 2Li3N
3Mg + N2 → Mg3N2
v. The hydroxides and carbonates of both Li and Mg decompose upon heating.
2LiOH → Li2O + H2O
Mg(OH)2 → MgO + H2O
Gp 1 Elements - 1H, 3Li, 11Na, 19K, 37Rb, 55Cs, 87Fr (Alkali Metals)
H = 1s1Li = 1s2 2s1Na = 1s2 2s2 2p6 3s1 K = 1s2 2s2 2p6 3s2 3p6 4s1 Rb = 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1Cs = [Xe] 6s1Fr = [Rn] 7s1
H = 1s1Li = 1s2 2s1Na = 1s2 2s2 2p6 3s1 K = 1s2 2s2 2p6 3s2 3p6 4s1 Rb = 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1Cs = [Xe] 6s1Fr = [Rn] 7s1
Gp 2 Elements - 2He, 4Be, 12Mg, 20Ca, 38Sr, 56Ba, 88Ra (Alkaline Earth Metals)
He = 1s2Be = 1s2 2s2Mg = 1s2 2s2 2p6 3s2 Ca = 1s2 2s2 2p6 3s2 3p6 4s2 Sr = 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2Ba = [Xe] 6s2Ra = [Rn] 7s2
He = 1s2Be = 1s2 2s2Mg = 1s2 2s2 2p6 3s2 Ca = 1s2 2s2 2p6 3s2 3p6 4s2 Sr = 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2Ba = [Xe] 6s2Ra = [Rn] 7s2
6Li (s) + N2(g) -------> 2Li3N (s)
