Study Notes
Atomic structure involves understanding the components of an atom and how they relate to the periodic table. The periodic table organizes elements based on their atomic number and properties.
- Pure Substance — a single element or compound not mixed with any other substance Example: Pure milk
- Mixture — made up of two or more substances physically joined, not chemically combined Example: Air
- Element — a substance made from only one type of atom Example: Sodium (Na)
- Compound — a substance made from two or more elements that undergo a chemical reaction Example: Water (H2O)
- Distillation — a method to separate a pure liquid from a mixture of liquids based on different boiling points Example: Separating ethanol from water
- Filtration — used to separate an insoluble solid from a liquid Example: Separating chalk from water
- Crystallisation — used to obtain a soluble salt from a solution Example: Obtaining copper sulfate crystals
- Paper Chromatography — a method to separate and identify substances in a mixture Example: Separating pigments in ink
- Proton Number — the number of protons in the nucleus of an atom Example: Hydrogen has a proton number of 1
- Nucleon Number — the total number of protons and neutrons in an atom's nucleus 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
- Relative Atomic Mass (Ar) — average mass of naturally occurring atoms of an element Example: Ar of chlorine is approximately 35.5
- Group 1 Elements — alkali metals that are highly reactive and have low melting points Example: Lithium, Sodium
- Group 7 Elements — halogens that are reactive non-metals Example: Chlorine, Bromine
- Group 0 Elements — noble gases that are inert and have full outer electron shells Example: Helium, Argon
Exam Tips
Key Definitions to Remember
- Pure substance: a single element or compound not mixed with others
- Mixture: two or more substances physically joined
- Element: a substance made from one type of atom
- Compound: a substance made from two or more elements chemically combined
Common Confusions
- Confusing elements with compounds; elements are single types of atoms, compounds are chemically combined elements
- Misunderstanding mixtures as compounds; mixtures are not chemically combined
Typical Exam Questions
- What is a pure substance? A single element or compound not mixed with others
- How can mixtures be separated? By physical methods like distillation or filtration
- What is the difference between an element and a compound? An element is made of one type of atom, a compound is made of two or more elements chemically combined
What Examiners Usually Test
- Understanding of atomic structure and subatomic particles
- Ability to explain methods of separating mixtures
- Knowledge of the periodic table and trends in groups and periods