Across
- 7. the weighted average mass of the atoms in a naturally occurring sample of the element
- 9. neutral subatomic particle that is a constituent of every atomic nucleus except ordinary hydrogen
Down
- 1. a collection of particles called protons
- 2. electron the electrons in the outermost shell, or energy level of an atom
- 3. The atomic number or nuclear charge number of a chemical element is the charge number of an atomic nucleus
- 4. he system of electrons surrounding the nucleus of an atom
- 5. a stable subatomic particle with a charge of negative electricity
- 6. stable subatomic particle that has a positive charge equal in magnitude to a unit of electron charge
- 8. the sum of the numbers of protons and neutrons present in the nucleus of an atom