Final answer:
Atoms of different elements can combine in simple whole number ratios to form chemical compounds. In chemical reactions, atoms are combined, separated, or rearranged.
Step-by-step explanation:
Atoms of different elements can combine in simple whole number ratios to form chemical compounds. In chemical reactions, atoms are combined, separated, or rearranged. The ratio of cations to anions in ionic compounds is determined by the need for the number of electrons lost by cations to be equal to the number of electrons gained by anions. This is required by the law of conservation of matter, where the total mass of the reactants must be equal to the total mass of the products.