Elements of Life

• Mass number is the number of protons and neutrons in the nucleus of an atom.
• Atomic number is the number of protons (or electrons) in an atom
• An isotope is an element with a different mass number as they have the same number of protons but different number of neutrons
• The relative atomic mass is the average mass of an atom of an element
• The number of particles is found by multiplying the number of moles by avogadros constant
• Empirical formula is the simplest whole number ratio of particles in a compound
• Molecular formula is the true number of atoms in a compound
• Percentage composition is found by dividing the Mr of the element by the Mr of the compund x 100
• n = cv
• mass = Mr x n
• Making a solution:

  1. Weigh sample bottle with sample in on a balance 2d.p.
  2. Transfer sample to beaker and reweigh bottle
  3. Record difference in mass
  4. Add distilled water and stir with glass rod until fully dissolved
  5. Transfer to volumetric flask and rinse beaker
  6. Make up to 250cm3 mark with distilled water and invert several times
• There are different orbitals in shells: s, p, d and f. The s-orbital is spherical and the p-orbital is dumbbell shaped
• Electrons in shells:

  • s = 2
  • p = 6
  • d = 10
  • f = 14
• Chromium and Copper are the two exceptions:

  • Chromium is 3d5 4s1 half is more stable
  • Copper is 3d10 4s1 full is more stable
• Fusion is when two lighter nuclei fuse to make one heavier nuclei
• Ionic bonding is an electrostatic attraction between two postive and negative ions and happens between a metal and non-metal. They can conduct electricity but only when molten or aqueous as ions can move
• Oppositely charged ions form electrostatic attractions and form a giant ionic lattice
• A covalent bond is an electrostatic attraction between two non-metals and can form multible bonds when multiple electrons are shared
• Dative covalent bonds are formed when the electrons in the bond are both from the same atom
• Linear molecules have 2 bonding pairs and a bond angle of 180º
• Bent molecules have 2 bonding and 1 lone pair and a bond angle of 104.5º
• Trigonal planar molecules have 3 bonding pairs and a bond angle of 120º
• Trigonal pyramidal molecules have 3 bonding and 1 lone pair and a bond angle of 107º
• Tetrahedral molecules have 4 bonding pairs and a bond angle of 109.5º
• Trigonal bipyrimidal molecules have 5 bonding pairs and bond angles of 90º and 120º
• Octahedral molecules have 6 bonding pairs and a bond angle of 90º
• Giant covalent structures like diamond (4 C-C bonds) and graphite (3 C-C bonds) are very strong and have high melting points
• Intermolecular forces between graphite layers are weak to they can slide over each other and therefore is useful as a lubricant
• Diamond is a tertahedral structure which is why it's so strong
• Metallic bonding is between two metals and is a giant lattice of strongly attracted electrons with a sea of delocalised electrons The greater the charge the stronger the attractive forces
• Ions that have a larger atomic radius have a weaker attraction
• Metallic structures are good at conducting electricity as the delocalised electrons can carry a charge
• Metals are malleable because the layers can slide over each other and they also have high melting points due to the electrostatic forces
• Melting points increase across a period and decrease down a group which is due to the type of bonding within the elements
• Group 2 carbonates are more thermally stable as you go down the group
• A higher charge density will result in a higher distorting effect on neighbouring negative ions in group 2 carbonates
• Solubility of group 2 carbonates decreases down the group
• Solubility of group 2 hydroxides increases down the group
• Ionisation energy increases across a period due to decreasing atomic radius but decreases down a group due to increasing atomic radius
• An acid is a proton (H+) donor