A water molecule consists of three atoms; an oxygen atom and two hydrogen atoms.
An atom of the water molecule consists of matter that has a nucleus in the center.
Each water atom contains an uncharged neutron, a positively-charged proton and a negatively-charged electron.
The number of electrons in an atom of the water molecule equals to the number of protons in the nucleus.
The attraction between the protons and electrons is what keeps an atom in the water molecule together.
The weight of a water molecule is determined by the atomic masses of the atoms that it is built of.
The atomic mass of each atom in the water is determined by the addition of the number of protons and neutrons in the nucleus, because the electrons hardly weigh anything.
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