Question

Can anyone tell me the Number of Ca, P, O, Mg and atoms in the following: Mg3(PO2) (s) + 3 Ca(NO2) 2 (aq)?

Answer 1

3 Mg atoms
1 P atom
2 O atoms

3 Ca atoms
6 N atoms
12 O atoms

Explanation:

Okay, so this is all about notation in chemistry.

The lowercase number immediately AFTER an atom is how many atoms of that element are in one molecule of the given substance.

I.e. `Mg_x` where `x` = no. of Mg atoms

The number BEFORE the molecule denotes how many molecules of a given substance (or element) are present in the reaction.

I.e. `xH_2O` where `x` = no. of `H_2O` molecules

If atoms are denoted in brackets within a molecule they form their own group within the molecule and thus the lowercase number AFTER the closed bracket

I.e. `Ca(NO)_x` where `x` = no. of (NO) groups within the molcule

In your example;

`Mg_3(PO_2)` (s) + `3Ca(NO_2)_2` (aq)

You have;
3 Mg atoms
1 P atom
2 O atoms

3 Ca atoms
6 N atoms
12 O atoms