Study Notes
The model of an atom describes its structure, consisting of a nucleus with protons and neutrons, and electrons in shells around it.
- Atom — the smallest unit of an element, consisting of a nucleus and electrons. Example: An oxygen atom has a nucleus with 8 protons and electrons in shells.
- Proton — a subatomic particle with a relative mass of 1 and a positive charge. Example: Found in the nucleus of an atom.
- Neutron — a subatomic particle with a relative mass of 1 and no charge. Example: Also located in the nucleus.
- Electron — a subatomic particle with a relative mass of 1/1836 and a negative charge. Example: Arranged in shells around the nucleus.
- Element — a substance made of atoms with the same number of protons. Example: Carbon is an element with atoms that all have 6 protons.
- Atomic Number — the number of protons in an atom's nucleus. Example: Oxygen has an atomic number of 8.
- Mass Number — the total number of protons and neutrons in an atom's nucleus. Example: Carbon has a mass number of 12.
Exam Tips
Key Definitions to Remember
- Atom: The smallest unit of an element.
- Proton: A positively charged subatomic particle in the nucleus.
- Neutron: A neutral subatomic particle in the nucleus.
- Electron: A negatively charged subatomic particle in shells around the nucleus.
- Element: A substance made of atoms with the same number of protons.
Common Confusions
- Confusing atomic number with mass number.
- Misunderstanding the arrangement of electrons in shells.
Typical Exam Questions
- What is the charge of a proton? Positive (+1)
- How are electrons arranged in an atom? In shells around the nucleus
- What defines an element? The number of protons in its atoms
What Examiners Usually Test
- Understanding of the structure of an atom
- Ability to identify subatomic particles and their properties
- Knowledge of how elements are represented on the Periodic Table