Atom

1. – A high-energy form of electromagnetic radiation.
3. – The neutral particle found in the nucleus of an atom.
6. – The building block of matter.
8. – Alpha particles are nuclei of this element.
11. – The type of charge of the alpha particles used in the gold foil experiment.
13. – The dense, tiny region at the center of an atom discovered by Rutherford.
14. – The scientist who conducted the gold foil experiment.
16. – The negatively charged particle orbiting the nucleus.
17. – Most of the atom is made up of this empty space.
19. – The positively charged particle in the nucleus of an atom.
20. – The type of radiation made of two protons and two neutrons.

2. – The smallest particle of an element.
4. – The central part of the atom.
5. – The energy emitted from unstable atomic nuclei.
7. – What happened to some alpha particles when they hit the gold foil.
9. – Rutherford's experiment used a thin sheet of this material.
10. – Rutherford proposed a planetary version of this for the atom.
12. – Radiation is a form of this.
15. – The type of radiation made of fast-moving electrons.
18. – Alpha particles have a positive one, while beta particles have a negative one.