Atoms

All matter is composed of atoms, which are the smallest particles in nature.
Each atom belongs to a specific element; there are nearly 100 natural elements.
Top six elements common in living organisms:
- Oxygen
- Carbon
- Hydrogen
- Nitrogen
- Calcium
- Phosphorus
Trace elements (e.g., iron) are also required for life.
Atoms consist of three subatomic particles and have two regions: the nucleus and an orbiting electron cloud.
Particles possess an electrical charge; opposite charges attract, and like charges repel.
Protons:
- Located in the nucleus.
- Positive charge.
Neutrons:
- Located in the nucleus.
- Neutral charge.
Electrons:
- Very small.
- Negative charge.
- Move rapidly around the nucleus.
- Held in orbit by attraction to the nucleus, forming an electron cloud.