Atoms

4. Atoms of the same element with different numbers of neutrons
6. Tiny negatively charged particles that orbit the nucleus
8. number Total count of protons and neutrons in an atom
10. mass Average mass of an element’s atoms considering its isotopes
11. A vertical column on the periodic table with elements that behave similarly
12. mass unit Unit used to measure the mass of atoms about one proton
13. Neutral particles in the nucleus that add mass but no charge
14. Small dense center of an atom holding protons and neutrons

1. atomic theory Early idea that matter is made of tiny, indivisible particles named after John Dalton
2. Positively charged particles in the nucleus that define the element
3. table Chart that arranges elements by atomic number and similar properties
5. A horizontal row on the periodic table
7. ray Beam used in old experiments that showed electrons exist
9. The smallest unit of an element that still has its properties
12. number Number of protons in an atom that identifies the element