Which of these are not true statements a compound? A compound's properties are usually not the same as the properties of the elements that make it up.
A compound always has the same composition.
A compound is made up of more than one type of atom.
A compound can have more than one chemical formula and still be considered the same compound.

A compound can have more than one chemical formula and still be considered the same compound.

Explanation:

Which of these are not true statements a compound?

A compound's properties are usually not the same as the properties of the elements that make it up.  TRUE. For instance, the salt NaCl has different properties than the solid metal Na and the gaseous nonmetal Cl₂.

A compound always has the same composition.  TRUE. The ratio of elements in a compound is constant.

A compound is made up of more than one type of atom.  TRUE. Unlike elements, compounds are formed by 2 or more elements.

A compound can have more than one chemical formula and still be considered the same compound. FALSE. Each compound can have only one chemical formula.

ionic bonds

In ionic bonds, electrons are gained by atoms and lost by others.