periodic table chem

• Atoms


  The basic building blocks of all matter
• Atoms


  • Made up of subatomic particles: neutrons (neutral charge, in nucleus), protons (positive charge, in nucleus), electrons (negative charge, surrounding nucleus in orbitals)
• Element


  A pure substance made from a single type of atom
• Types of elements


  • Monoatomic
  • Molecules
  • Lattice
• Molecule


  Two or more atoms chemically bonded together
• Compound


  Made up of more than one type of atom
• Atomic number


  The number of protons in an element
• Relative atomic mass


  The number of protons and neutrons found in the nucleus of an atom
• Determining number of protons, neutrons and electrons in oxygen

  1. Atomic number = 8

  2. Mass number = 16

  3. Protons = 8

  4. Electrons = 8

  5. Neutrons = Mass number - Atomic number = 16 - 8 = 8
• Determining number of protons, neutrons and electrons in aluminium

  1. Atomic number = 13

  2. Mass number = 27

  3. Protons = 13

  4. Electrons = 13

  5. Neutrons = Mass number - Atomic number = 27 - 13 = 14
• Cation


  Positive ion that loses electrons to obtain a full outer shell
• Anion


  Negative ion that gains electrons to obtain a full outer shell
• Forming sodium ion (Na+)

  1. Atomic number = 11

  2. Number of electrons = 11

  3. Number of protons = 11

  4. Electron configuration: 2,8,1 needs to lose 1 electron, therefore becomes Na+
• Forming fluoride ion (F-)

  1. Atomic number = 9

  2. Number of electrons = 9

  3. Number of protons = 9

  4. Electron configuration: 2,7 needs to gain 1 electron, therefore becomes F-
• Isotopes


  Have the same number of protons but a different number of neutrons
• Bohr model of the atom

  • Electrons revolve rapidly around the nucleus in fixed circular paths called energy levels or shells
  • Energy levels represented by numbers 1, 2, 3, 4 or letters K, L, M, N, counted from the center outwards
• Maximum number of electrons in each energy level

  • 1 (K shell) - 2 electrons
  • 2 (L shell) - 8 electrons
  • 3 (M shell) - 18 electrons
  • 4 (N shell) - 32 electrons
• Rules for electrons occupying shells

  • Each shell contains a maximum number of electrons

  2. Lower energy shells fill first

  3. Electrons fill in a particular order
• Emission spectrum


  When an element is heated, it gives off electromagnetic radiation or light. This light passed through a prism produces a spectrum with a black background and coloured lines, which is unique for each element and can be used to identify it.
• Ground state


  The lowest energy level where electrons are most stable
• Excited state


  A higher energy level where electrons become less stable after absorbing energy
• Schrödinger model of the atom

  • Electrons occupy regions around the nucleus called orbitals, not fixed orbits

  Orbitals have a maximum of 2 electrons due to the Pauli exclusion principle

  Electrons still occupy shells of varying energy levels
• Order of filling subshells

  • 1s
  • 2s
  • 2p
  • 3s
  • 3p
  • 4s
  • 3d
  • 4p
  • 5s
  • 4d
  • 5p
  • 6s
  • 4f
  • 5d
  • 6p
• Valence electrons


  Electrons in the outermost shell that require the least energy to be removed
• Valence shell


  The outermost shell of an atom
• Ground state


  Electrons fill subshells in order of increasing energy
• Excited state


  Electrons don't fill subshells in order of increasing energy