The alpha particles that were fired at the gold foil were positively charged. ... These experiments led Rutherford to describe the atom as containing mostly empty space, with a very small, dense, positively charged nucleus at the center, which contained most of the mass of the atom, with the electrons orbiting the nucleus.
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The answer is 80 atomic mass
<span>These atoms are known as valence atoms.</span>
Chlorine is a halogen and all halogens and oxygen, nitrogen and hydrogen are diatomics