Study Notes
The structure of an atom includes a central nucleus containing protons and neutrons, surrounded by electrons in shells. The periodic table arranges elements by increasing proton number, with similar properties grouped together.
- Atom — the smallest unit of matter, consisting of protons, neutrons, and electrons.
Example: Hydrogen atom has 1 proton and 1 electron. - Proton Number — also known as atomic number, it is the number of protons in the nucleus of an atom.
Example: Carbon has a proton number of 6. - Nucleon Number — also known as mass number, it is the total number of protons and neutrons in the nucleus.
Example: Oxygen has a nucleon number of 16. - Electron Configuration — the arrangement of electrons in an atom's energy levels or shells.
Example: Sodium has an electron configuration of 2, 8, 1. - Energy Levels — specific distances from the nucleus where electrons orbit, also known as principal quantum shells.
Example: The first energy level can hold up to 2 electrons.
Exam Tips
Key Definitions to Remember
- Proton number is the number of protons in an atom's nucleus.
- Nucleon number is the total number of protons and neutrons in the nucleus.
- Electron configuration is the arrangement of electrons in energy levels.
Common Confusions
- Confusing proton number with nucleon number.
- Misunderstanding the arrangement of electrons in shells.
Typical Exam Questions
- What is the proton number of an element with 6 protons?
Answer: 6 - How many electrons can the second energy level hold?
Answer: 8 - What is the electron configuration of an element with atomic number 10?
Answer: 2, 8
What Examiners Usually Test
- Understanding of atomic structure and subatomic particles.
- Ability to determine electron configurations.
- Knowledge of how elements are arranged in the periodic table.