Definitions

• Anion

  a negatively charged ion. Formed when an atom gains at least one electron
• Atom

  The smallest part of an element that can exist. All substances are made up of atoms
• Atomic nucleus

  Positively charged object composed of protons and neutrons at the centre of every atom with 1 or more electrons orbiting it
• Atomic number

  The number of protons in the nucleus
• Avogadro's constant

  The number of atoms, molecules or ions in a mole of a given substance
• Cation

  A positively charged ion. Formed when an atom loses at least 1 electron
• Compound

  A substance made up of 2 or more types of atoms chemically combined together
• Conductor

  A material that contains charged particles which are free to move to carry electrical or thermal energy
• Conservation of mass

  A law which states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants
• Covalent bond

  A shared pair of electrons between two non-metals
• Dalton model

  Dalton described atoms as solid spheres, stating that different spheres made up the different elements
• Diamond

  A giant covalent structure which is made up of carbon atoms each of which form 4 covalent bonds with four other carbon atoms
• Electron

  Negatively charged subatomic particle which orbit the nucleus at various energy levels. Very small relative mass (negligible)
• Electron shell

  Different energy levels in atoms occupied by electrons
• Electrostatic forces

  The strong forces of attraction between oppositely charged ions
• Element

  A substance made up of only 1 type of atom
• Empirical formula

  The simplest whole number ratio of atoms of each element in a compound
• Fullerenes

  Molecules of carbon atoms with hollow shapes. The structures are based on hexagonal rings of carbon atoms but they may also contain rings with 5 or 7 carbon atoms. E.g., graphene and C60
• Giant covalent molecule

  Molecules containing many atoms covalently bonded together
• Graphene

  A single layer of graphite with properties that make it useful in electronics and composites
• Graphite

  A giant covalent structure which is made up of carbon atoms each of which form 3 covalent bonds with three other carbon atoms. The atoms form layers of hexagonal rings which have no covalent bonds between them. There is one delocalised electron per carbon atom which is free to move to carry charge
• Group

  A column of the periodic table. Elements in the same group have similar chemical properties
• Intermolecular forces

  The forces which exist between molecules. The strength of the intermolecular forces impact physical properties like boiling/melting point
• Ion

  An atom or molecule with an electric charge due to the loss or gain of electrons
• Ionic bond

  The bond formed between the oppositely charged ions when a metal atom loses electrons to form a positively charged ions and a non-metal gains these electrons to form a negatively charged ion
• Ionic compound

  Chemical compound formed of oppositely charged ions, held together by strong electrostatic forces
• Isotope

  Atoms of the same element with the same number of protons but a different number of neutrons
• Lattice

  A repeating regular arrangement of atoms/ions/molecules. This arrangement occurs in crystal structures
• Limiting reactant

  The reactant that is completely used up since it limits the amount of products formed
• Mass number

  The total number of protons and neutrons in the nucleus
• Metallic bond

  The bonds present in metals between the positive metal ions and negatively charged electrons
• Metals

  Elements that react to form positive ions. Found to the left and towards the bottom of the periodic table
• Mole

  The unit for amount of substance. The symbol for the unit mole is mol
• Molecular formula

  The actual ratio of atoms of each element present in a compound
• Molecule

  A group of at least 2 atoms held together by covalent bonds
• Neutron

  Neutral subatomic particle present in the nucleus of the atom. Relative mass of 1
• Non-metals

  Elements that react to form negative ions. Found towards the right and top of the periodic table
• Period

  A row of the periodic table. Elements in the same period have the same number of electron shells
• Periodic table

  Table of elements arranged in order of increasing atomic number and such that elements with similar properties are in the same column (group)
• Polymers

  Large long-chain molecules made up of lots of small monomers joined together by covalent bonds