In what type of ratios do atoms combine to form compounds

whole number ratios

Explanation:

Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Copper

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass. It can be decomposed into simpler constituents using chemical reactions. Example: water

Thus the ratio of hydrogen and oxygen is 2: 1 and is a whole number ratio.

a electronegativity decreases beacuse the size of nucleus is bigger.