Advanced Topics
In a nutshell: Atoms are made up of protons, neutrons, and electrons, and their arrangement explains chemical behavior.
## Peeking Inside the Atom
Atoms are made up of even smaller particles called **protons**, **neutrons**, and **electrons**.
- **Protons** have a positive charge and are found in the atom's center, called the nucleus.
- **Neutrons** have no charge (they're neutral) and are also in the nucleus.
- **Electrons** are negatively charged and whiz around the nucleus in regions called electron shells.
The number of protons determines what element an atom is. For example, hydrogen has 1 proton, while oxygen has 8.
### Atomic Number and Mass Number
- **Atomic number:** Number of protons in an atom.
- **Mass number:** Number of protons plus neutrons.
### Why Does the Structure Matter?
The arrangement of electrons affects how atoms join together to form molecules. The atomic structure explains why elements react in certain ways and helps us create new materials.
Atomic Number = Number\ of\ Protons
Examples
- Carbon atoms have 6 protons, 6 neutrons, and 6 electrons.
- Helium's full outer shell makes it very stable and unreactive.
Key terms
- Proton
- A positively charged particle in the nucleus of an atom.
- Neutron
- A neutral particle in the nucleus of an atom.
- Electron
- A negatively charged particle that orbits the nucleus.
- Nucleus
- The center of an atom, containing protons and neutrons.
- Atomic Number
- The number of protons in an atom, which determines the element.