module 2 definitions

• Atomic Number


  The number of protons in the nucleus of an atom
• Bohr Model


  Describes an atom as a small dense nucleus with electrons orbiting around the nucleus. This model explains different periodic properties of atoms.
• Electron


  A negatively charged subatomic particle which orbits the nucleus at various energy levels. The relative mass of an electron is 1/1836.
• Ion


  A charged atom or molecule
• Isotopes


  Atoms of the same element with the same number of protons and electrons but different numbers of neutrons. Isotopes of an element have different masses.
• Mass Number


  The total number of protons and neutrons in the nucleus of an atom
• Mass Spectrometry


  An instrument which gives accurate information about relative isotopic mass and the relative abundance of isotopes
• Neutron


  A neutral subatomic particle found in the nucleus of an atom. The relative mass of a neutron is 1.
• Proton


  A positively charged subatomic particle found in the nucleus of an atom. The relative mass of a proton is 1.
• Relative Abundance


  The amount of one substance compared with another
• Relative Atomic Mass


  The weighted mean mass of an atom compared with 1/12th mass of an atom of carbon-12
• Relative Isotopic Mass


  The mass of an atom of an isotope compared with 1/12th mass of an atom of carbon-12
• Relative Formula Mass


  The mass of the formula unit of a compound with a giant structure. For example, NaCl has a relative formula mass of 58.44 g mol^-1.
• Relative Molecular Mass (Mr)


  The mass of a simple molecule
• Ammonium ion


  An ion with the formula NH4+
• Carbonate


  An ion with the formula CO3^2-
• Hydroxide


  An ion with the formula OH-
• Ionic Compound


  A compound which is made up of oppositely charged ions that are held together by electrostatic forces
• Nitrate


  An ion with the formula NO3-
• Silver ion


  Has the formula Ag+
• State symbols


  Symbols within a chemical equation which indicate the state of each compound under the reaction conditions. (g) gaseous, (l) liquid, (s) solid and (aq) aqueous.
• Sulfate


  An ion with the formula SO4^2-
• Zinc ion


  Has the formula Zn^2+
• Amount of substance


  The quantity that has moles as its units, used as a way of counting atoms. The amount of substance can be calculated using mass (n = m/M), gas volumes (n = pV/(RT)) or solution volume and concentration (n = CV).
• Anhydrous


  A crystalline compound containing no water
• Atom Economy


  A measure of the amount of starting materials that end up as useful products. A high atom economy means a process is more sustainable as there is less waste produced.
• Avogadro Constant (NA)


  The number of particles per mole of substance (6.02 x 10^23 mol^-1)
• Composition by mass


  The relative mass of each element in a compound
• Empirical Formula


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


  A crystalline compound that contains water
• Ideal Gas


  A gas which has molecules that occupy negligible space with no interactions between them. The ideal gas equation is: pV = nRT.
• Molar Gas Volume


  The volume of 1 mole of gas (units: dm^3 mol^-1)
• Molar Mass


  Mass per mole of a substance (units: g mol^-1)
• Mole (mol)


  The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of carbon-12 isotope
• Molecular Formula


  The number and type of atoms of each element in a molecule
• Percentage Yield


  The percentage ratio of the actual yield of product from a reaction compared with the theoretical yield
• Relative Molecular Mass


  The average mass of one molecule of an element or compound compared to 1/12th the mass of an atom of carbon-12
• Stoichiometry


  The relative quantities of substances in a reaction
• Water of Crystallisation


  Water molecules that form part of the crystalline structure of a compound
• Acid


  Compounds that release H+ ions in aqueous solution. Common acids include: HCl, H2SO4, HNO3 and CH3COOH.