1.
₇N⁻³ => 1s2 2s2 2p6
E⁺ => 1s2 2s2 2p6 3s1 => gr. 1 (I-A), p. 3
2.
1 mol Cl2 ..... 2x6,022x10²³ atomi Cl ..... 2x17x6,022x10²³ e-
3.
3Ca = 3x40 = 120 g
(PO4)2 = 2P + 8O = 2x31 + 8x16
=> Ca:P:O = 120:62:128 /:2 = 60:31:64
4.
miu.CaCO3 = 40+12+4x16 = 100 g/mol
=> 100 g ......................... 40 g Ca
300 g ........................ x = 120 g Ca