Question

1. a(n)______is a substance of two or more atoms held together with chemical bonds. proton element molecule ion isotope

Explanation:

• A proton is a sub - atomic particle in the nucleus of an atom.
• An element is a pure substance made of only one type of atom.
• A molecule is defined as a substance of two or more atoms held together by chemical bonds.
• An ion is an atom or molecule with a net electric charge due to loss or gain of electrons.
• An isotope is an atom of the same element with a different number of neutrons.

Answer:

molecule