Study Notes
Atoms are made up of protons, neutrons, and electrons, with protons and neutrons located in the nucleus and electrons in shells around the nucleus. Elements are pure substances made of one type of atom, compounds are substances formed by chemical reactions between elements, and mixtures are combinations of substances that do not chemically react.
- Atom — the smallest unit of an element, consisting of protons, neutrons, and electrons Example: Hydrogen atom
- Element — a substance made from only one type of atom Example: Carbon (C)
- Compound — a substance made from two or more elements that undergo a chemical reaction Example: Water (H2O)
- Mixture — a combination of two or more substances that do not chemically react Example: Air
- Isotope — atoms of the same element with the same number of protons but different numbers of neutrons Example: Carbon-12 and Carbon-14
- Ionic Bond — a bond formed by the electrostatic attraction between oppositely charged ions Example: Sodium Chloride (NaCl)
- Covalent Bond — a bond formed by the sharing of electrons between atoms Example: Water (H2O)
- Metallic Bond — a bond formed by the attraction between positively charged metal ions and delocalized electrons Example: Copper (Cu)
Exam Tips
Key Definitions to Remember
- Atom: the smallest unit of an element
- Element: a substance made from only one type of atom
- Compound: a substance made from two or more elements that undergo a chemical reaction
- Mixture: a combination of substances that do not chemically react
- Isotope: atoms of the same element with different numbers of neutrons
- Ionic Bond: electrostatic attraction between oppositely charged ions
- Covalent Bond: sharing of electrons between atoms
- Metallic Bond: attraction between metal ions and delocalized electrons
Common Confusions
- Confusing atomic number with mass number
- Mixing up ionic and covalent bonds
- Misunderstanding the difference between compounds and mixtures
Typical Exam Questions
- What is an isotope? Atoms of the same element with different numbers of neutrons
- How do ionic bonds form? Through the electrostatic attraction between oppositely charged ions
- What is the difference between a compound and a mixture? Compounds are chemically bonded; mixtures are not
What Examiners Usually Test
- Understanding of atomic structure and subatomic particles
- Ability to distinguish between elements, compounds, and mixtures
- Knowledge of different types of chemical bonds and their properties