Atoms!

4. A subatomic particle which helps keep an atom stable
5. Niels Bohr proposed in his model that electrons move around in _____ of fixed sizes and energies
7. The center of an atom that contains protons and neutrons
10. an average mass of all isotopes. Found on the atomic symbols on the periodic table (two words)
12. Discovered electrons. Created the "plum pudding model"

1. In a ______ atom, the number of protons is equal to the number of electrons.
2. The atomic number tells us the number of _____ within that element
3. An atoms has a mass of 16amu. amu stands for atomic mass ____
6. the addition of protons and neutrons is called the mass ____
8. The smallest subatomic particle
9. _____ Theory started by Dalton which states that all elements are made up of atoms
11. The one or two letters on the periodic table that represent an element is called an element ______