How do I find out the number of protons, neutrons and electrons in a atom?

I mean, I have a science exam tomorrow, and I specialize in science, and I wanted to know this for sure... How do I find the number of electrons in a atom? I thought it was the atomic number is how much protons and neutrons in the atom, as in, atomic number = 1, protons = 1, neutrons = 1. and electrons were the... show more I mean, I have a science exam tomorrow, and I specialize in science, and I wanted to know this for sure... How do I find the number of electrons in a atom? I thought it was the atomic number is how much protons and neutrons in the atom, as in, atomic number = 1, protons = 1, neutrons = 1. and electrons were the weight, as in, atomic mass = 4, eletrons = 4. Is this correct? or am I doing this wrong? If so, Can you explain how to do it?
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