Unit 2 and 3: terms to remember (fixed)

• Protons

  Particles with a relative mass of 1, a positive charge of 1+, located in the nucleus.
• Neutrons

  Particles with a relative mass of 1, no charge (0), located in the nucleus.
• Electrons

  Particles with a relative mass of 1/1836 or negligible, a negative charge of 1-, located in shells.
• Isotopes

  Atoms of the same element with different numbers of neutrons and masses.
• Mass Number

  Sum of protons and neutrons in the nucleus.
• Relative Isotopic Mass

  Mass of an isotope relative to 1/12th of the mass of an atom of carbon-12.
• Relative Atomic Mass

  Weighted mean mass of an element's atom relative to 1/12th of the mass of an atom of carbon-12.
• Mass Spectrometer


  Instrument used to determine the percentage abundance of isotopes in a sample.
• Reduction

  Gaining electrons
• Oxidation

  Losing electrons
• Electron Configuration

  Shells are energy levels; the principle quantum number, n, determines the shell number; Maximum number of electrons = 2n^2
• Atomic Orbital


  A region around the nucleus that can hold up to 2 electrons
• Sub-shell


  A group of the same type of orbitals within a shell
• Relative Energy of an s and a p Orbital

  The p orbitals have the same energy
• Rules for Filling of Orbitals

  Orbitals fill in order of increasing energy; Electrons pair with opposite spins; Orbitals with the same energy are occupied singly first
• Ionic Bonding


  Electrostatic attraction between positive and negative ions
• Covalent Bonding


  Electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
• Dative Covalent Bond


  Forms when 1 atom provides both electrons to form a covalent bond
• Electronegativity


  Measures the attraction of a bonded atom for the pair of electrons in a covalent bond
• Polar Bonds


  Form when one atom is more electronegative than the other and the electron pair is not shared equally
• Polar Molecules

  Form when bonds are polar and the molecule is not symmetrical, so the dipoles do not cancel out
• Intermolecular Forces


  Weak attractions between dipoles of different molecules
• Simple Molecular Lattice


  In the solid state, simple molecules form a regular structure held by weak intermolecular forces
• First ionisation energy


  Energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
• Successive ionisation energies


  Can provide information about the number of electrons in the outer shell, the group of the element in the PT, the identity of an element
• Trend in 1st IE down the group

  1st IE down the group decreases
• Trend in 1st IE across a period

  1st IE down the group generally increases
• In which groups the 1st IE drops

  In group 13 and 16
• Giant metallic lattice


  Structure and bonding changes across period
• Metallic bonding

  An electrostatic attraction between positive ions and delocalised electrons
• Metals conduct electricity because...

  The delocalised electrons are mobile both in solid and liquid states
• Metals have high melting and boiling points because...

  The electrostatic attraction between cations and delocalised electrons is very strong
• Substances that have a giant covalent lattice are...

  Carbon, Silicon, Silicon dioxide, SiO2
• Giant covalent lattices have high melting and boiling points because...


  Giant covalent lattices don't conduct electricity because there are no charged particles that are mobile
• Trend in the melting points across a period

  Caused by the trend in breaking all the covalent bonds in giant covalent lattices
• What happens to group 2 elements (in terms of electrons) when they react with O2, acids and water?

  they lose electrons
• What is/are the product(s) of the reaction of a gr. 2 element with water?

  A hydroxide and hydrogen gas
• What are the products of the reaction of a gr. 2 element with an acid?

  A salt and hydrogen gas
• What is the trend in reactivity of group 2 elements?

  Reactivity increases down the group
• What is the trend in solubility of gr. 2 hydroxide in water down the group?

  It increases