| A | B |
|---|
| Atom | The smallest part of an element that still has the properties of that element. |
| Element | A pure substance made of only one kind of atom. |
| Nucleus | The center of an atom that contains protons and neutrons. |
| Proton | A positively charged particle found in the nucleus of an atom. |
| Neutron | A particle with no charge (neutral) found in the nucleus of an atom. |
| Electron | A negitivley charged particle that moves around the nucleus in energy levels or shells. |
| Atomic Number | The number of protons in an atom's nucleus in energy levels or shells. |
| Atomic Mass | The total number of protons and neutrons in the nucleus of an atom. |
| Energy Level (or Electron Shell) | The area around the nucleus where the electrons are likely to be found. |
| Bohr Model | A diagram that shows an atoms nucleus and electrons in circular energy levels around it. |
| Electron Cloud | The region around the nucleus where the electrons are likely to be found; shows that electrons move quickly and randomly. |
| Isotope | Atoms of the same element that have different numbers of neutrons. |
| Ion | An atom that has gained or lost electrons, giving it a positive or negative charge. |
| Subatomic Particle | A particle smaller than an atom (protons, neutrons, and electrons). |
| Periodic Table | A chart that organizes all known elements by their properties, atomic number, and atomic mass. |
| Chemical Symbol | The one- or two-letter abbreviation that represents an element (like H for hydrogen). |
| Mass Number | The total number of protons and neutrons in an atom's nucleus (often the same as atomic mass rounded to a whole number). |
| Neutral Atom | An atom with the same number of protons and electrons, so the charges balance out. |
| Change | A property of matter that causes it to attract or repel other particles; can be positive, negative, or neutral. |
| Model | A simple representation used to explain the structure or behavior of something complex, like an atom. |
