Topic 1 – Key Concepts in Chemistry

Balancing Chemical Equations

Balancing chemical equations ensures the same number of each type of atom on both sides of the reaction

History of the Atom

The history of the atom includes Dalton; Thomson; Rutherford; and Bohr models describing atomic structure

Atoms

An atom is the smallest particle of an element; consists of a nucleus and electrons in shells

Elements

An element contains only one type of atom; isotopes have the same number of protons but different neutrons

Relative Atomic Mass (Ar)

Relative atomic mass is the weighted average of isotopes compared with 1/12th of a carbon-12 atom

Compounds

Compounds contain two or more elements chemically combined in fixed ratios

Molecules

A molecule is two or more atoms bonded together; can be the same or different elements

Mixtures

A mixture contains two or more substances not chemically bonded; separated physically

Periodic Table Development

The periodic table is arranged by increasing atomic number; groups have similar properties

Electronic Structure

Electronic structure describes the arrangement of electrons in shells

Formation of Ions

Ions are formed when atoms lose or gain electrons to achieve a full outer shell

Metals & Non-Metals

Metals tend to lose electrons; non-metals tend to gain electrons

Ionic Bonding

An ionic bond forms from electrostatic attraction between positive and negative ions

Ionic Compounds

Ionic compounds have a giant lattice structure; high melting points; conduct electricity when molten or in solution

Covalent Bonding

A covalent bond is the sharing of electron pairs between atoms

Types of Covalent Structures

Covalent structures can be simple molecules; giant covalent structures; or macromolecules

Diamond & Graphite

Diamond is hard; does not conduct; Graphite is soft; conducts due to delocalised electrons

Graphene & Fullerenes

Graphene is a single layer of graphite; Fullerenes are spherical carbon molecules with unique properties

Metallic Bonding

Metallic bonding consists of a lattice of positive ions with delocalised electrons; explains conductivity

Conservation of Mass

Conservation of mass states mass is neither created nor destroyed in a reaction

Relative Formula Mass (Mr)

Relative formula mass is the sum of relative atomic masses of all atoms in a compound

Moles & Mass

Moles = mass divided by Mr

Calculating Mass in Reactions

The mass of a substance in a reaction can be calculated using moles and Mr

Molecular & Empirical Formulas

Molecular formula shows actual atoms; empirical formula shows simplest ratio

Limiting Reactants

The limiting reactant is used up first; determines maximum product