1. From the atomic number, the number of protons in an atom’s nucleus.
2. Silicon
3. You can find this from the atomic number. An atom has no overall charge, so it must have an equal number of positive protons and negative electrons. Therefore, the number of electrons surrounding the nucleus must equal the number of protons found in the nucleus, which is the atomic number.
4. Potassium
5. The mass number of an atom of an element is the combined number of protons and neutrons. So, if you subtract the number of protons—equal to the atomic number—from an atom’s mass number, the result is the number of neutrons present in the nucleus.
6. Hydrogen
7. 30
8. 17 protons, 18 neutrons, 17 electrons