Study Notes
Atoms are made up of three subatomic particles: protons, neutrons, and electrons. The nucleus contains protons and neutrons, while electrons orbit in shells around the nucleus. Elements are organized in the periodic table by their proton number, which determines their chemical properties. Proton — positively charged particle in the nucleus.
Example: Hydrogen has 1 proton.
- Neutron — neutral particle in the nucleus.
Example: Carbon has 6 neutrons. - Electron — negatively charged particle orbiting the nucleus.
Example: Oxygen has 8 electrons. - Proton Number — number of protons in an atom's nucleus, also known as the atomic number.
Example: Helium has a proton number of 2. - Nucleon Number — total number of protons and neutrons in an atom's nucleus, also known as the mass number.
Example: Carbon-12 has a nucleon number of 12. - Isotopes — atoms of the same element with the same number of protons but different numbers of neutrons.
Example: Carbon-12 and Carbon-14 are isotopes of carbon.
Exam Tips
Key Definitions to Remember
- Proton: positively charged particle in the nucleus
- Neutron: neutral particle in the nucleus
- Electron: negatively charged particle orbiting the nucleus
- Proton Number: number of protons in an atom's nucleus
- Nucleon Number: total number of protons and neutrons in an atom's nucleus
Common Confusions
- Confusing atomic number with mass number
- Misunderstanding isotopes as different elements
Typical Exam Questions
- What is the charge of a proton?
Positive (+1) - How do you calculate the number of neutrons in an atom?
Subtract the atomic number from the mass number - What is an isotope?
Atoms with the same number of protons but different numbers of neutrons
What Examiners Usually Test
- Understanding of subatomic particles and their charges
- Ability to calculate the number of neutrons
- Knowledge of how elements are arranged in the periodic table