Chemistry 2A

Chemistry 2A

Bonding and Structure
1. Ionic Bonding - metal atoms lose electrons and become positively charged. Non-metal atoms gain electrons and become negative.
2. Covalent bond is between non-metals, which share electrons. They are very strong, with low melting and boiling points.
3. Macromolecules have giant covalent structures. Arranged in giant lattices, they have very high melting and boiling points.
4. Thermosoftening polymers soften and can be shaped when hot, but harden when cooled, because they have no cross links to hold the shape together.
5. Thermosetting polymers cannot be reshaped or softened once moulded, because they have cross links.
6. Metals are good conductors of electricity because of their free electron.
7. Ionic compounds don't conduct electricity when in solid form because their lattice form means ions cannot move around.
8. Graphite conducts well because of its delocalised electrons.
Atoms
1. The mass number is total number of protons and neutrons
2. Atomic number is number of protons
3. Compounds are chemically bonded
4. Isotopes are different atomic forms of the same element, which have the same number of protons but a different number of neutrons
  1. Carbon-12 and Carbon-14 are a pair of isotopes
5. Ions are atoms that have lost or gained at least one electron
6. In ionic bonding metals lose electrons to form positive ions, non-metals gain electrons to form negative ions
Relative Mass and Percentage Yield
1. Relative Atomic Mass is the same as the mass number of an element, they are added together when there is more than one atom
2. Number of moles = mass in g/ relative formula mass
3. Percentage mass of an element in a compound = relative atomic mass of that element/relative formula mass of the whole compound X100
4. Empirical formula is an element in its simplest form, so list all the elements in a compound and write their experimental masses. Divide each mass by the relative atomic mass for that element. Turn the answers into a ratio, then simplify the ratio as much as possible
5. Calculating masses in reactions - write out the balanced equation, work out the relative formula mass for the parts you need, divide to get one part then multiply to get all
6. Percentage yield compares the actual outcome with the predicted outcome. Percentage yield = actual yield/predicted yield X100
  1. Will always be under 100%

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