A1 - Atomic structure and bonding
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Define isotopes
isotopes are atoms of the same element with different numbers of neutrons and different masses
Define relative isotopic mass
the mass of an isotope relative to 1/12th of the mass of an atom an carbon-12
Define relative atomic mass (Ar)
the weighed mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12
What does the weighted mean mass take account of?
• the percentage of abundance of each isotope • the relative isotopic mass of each isotope
What is the mass of carbon-12 isotope defined as?
12 atomic mass units (12u)
What is the standard mass for atomic mass?
1u –> the mass of 1/12th of an atom of carbon-12 –> 1u is approximately the mass of a proton or a neutron
Define the term orbital
a region around the nucleus that can hold up to two electrons, with opposite spins
What are the different types of orbital?
s p d f
How many electrons can fill the first 4 shells?
1 - 2 2 - 8 3 - 18 4 - 32
What is the shape of a s-orbital?
spherical
What is the shape of a p-orbital?
dumbbell shaped
What is the number of orbitals making up s- sub shells?
1
What is the number of orbitals making up p- sub shells?
3
What is the number of orbitals making up d- sub shells?
5
What is the number of electrons that can fill s- sub shells?
2
What is the number of electrons that can fill p- sub shells?
6
What is the number of electrons that can fill d- sub shells?
10
What are the three principles for working out electron configurations?
• electrons fill orbitals in order of increasing energy –> 4s sub-shell has a lower energy than 3d sub-shell, so 4s is filled before 3d • an orbital can contain a maximum of two electrons with opposite spins • for orbitals of the same energy, orbitals are occupied singly before pairing
Define ionic bonding
ionic bonding is the electrostatic attraction between positive and negative ions
What structure do ionic bonds form?
Giant ionic lattice each ion is surrounded by ions of opposite charge strongly attracted in all directions
Properties of ionic compounds - melting and boiling points
high MP and BP lots of energy required to break all the strong ionic bonds in the giant ionic lattice
What does the strength of ionic bonding depend on?
• smaller ions form stronger ionic bonds • more highly-charged ions form stronger bonds
Properties of ionic compounds - solubility
ionic compounds are soluble in polar solvents like water insoluble in non-polar solvents like hydrocarbons
Properties of ionic compounds - electrical conductivity
• do not conduct electricity when solid because the ions are in fixed positions in the giant ionic lattice • do conduct electricity when molten or dissolved in water, giant ionic lattice has been broken down and the ions can now move