2.2 Electrons, bonding and structure Flashcards
energy levels
As electrons are removed from an atom, the subsequent ionisation energy will have to be greater
Ionisation energy- the minimum amount of energy required to remove an electron from an isolated atom/molecule
1st shell- 2
2nd shell- 8
3rd shell- 18
what on a graph determines a sub-shell
The first ionisation energy of elements reveal minor jumps as the shells are further divided into subshells.
Large drop indicates a new shell. The 1st small drop indicates the 1st subshell, the 2nd drop indicates the 1st subshell is half-filled.
how do you name the sub-shells
Electrons further from the nucleus are in a higher energy state/level.
The lowest energy state in any energy level is the s
sub-shell, then PDF.
what are orbitals
A region around the nucleus that can hold up to 2 electrons with opposite spins.
Each sub-shell contains a different number of orbitals.
Different types of orbitals have different shapes
S- orbitals are spheres and P-orbitals are dum-bells.
electron repulsion theory
States that electron pairs repel each other to be as far away from each other as possible.
[see physical flashcards for table]
what is an electron pair
two electrons occupying the same orbital in an atom or molecule
what has the most repulsion (from most to least)
- 2 lone pairs
- Lone pair and bonded pair
- 2 bonded pairs
The number of bonded and lone pairs
determines a molecules shape
how do you make a molecule more stable via sub-shell overlap
The further from the nucleus, the closer together the energy levels become. The 4s sub-shell is therefore at a lower energy level than the 3rd subshell
totally full sub-shells are very stable and the energy difference between :
A ½ full and full s-orbital is small
An almost ½ full and ½ full d-orbital is big.
So, by moving an electron from 4s to 3d, orbitals, it becomes stable
how do you fill orbitals
Fill from the lowest energy level
2 electrons can be in orbital but must have opposite spins
Only pair up if no other orbitals are present.
how do you abbreviate
Look at the noble gas that comes before it.
E.g. Magnesium [Ne] 1S2, 2S2, 2P6
what is ionic bonding
Transfers electrons and us between metals and on-metals.
A metal atom loses one or more of its electrons from its valence shell and is transferred to the non-metal
the resultant ions have the electronic structure of a noble gas.
Ions form when atoms gain/lose electrons to become isoelectric with a noble gas.
why is high melting points a typical property of ionic lattices
ionic bonds are strong and occur throughout the giant lattice, so in order to melt an ionic solid, all the bonds have to be broken. This uses a lot of energy
why is poor conductor when solid a typical property of ionic lattices
the ions are held in a fixed position and cannot move. There is no mobile charge carriers, hence poor conductibility
why is good conductor when molten or dissolved in water a typical property of ionic lattices
when melted or dissolved in water, the ions are mobile and free to move.
why is soluble in water or polar solvents a typical property of ionic lattices
water has dipoles like ionic solids do.
why is water as an anomalous point
Due to its hydrogen bonds, water is less dense as a solid.
Liquid water- hydrogen bonds are constantly being broken and reformed
Solid water- molecules arranged in hexagonal rings to maximise the amount of stable hydrogen bonds.
The more open interlocking ringed structures, the larger the volume, lowering the density
what are permanent dipole-dipole intermolecular bonds
Exists between 2 permanently polar molecules due to electronegativity. Has a + dipole on one side, a – dipole on the other, the molecules would line up throughout a liquid/solid in this fashion
what are induced dipole-dipole intermolecular bonds
If 1 molecule has a temporary dipole, the partial charge will exert a force on nearby molecules. The partial charge will exert a force on nearby molecules ( or attract it).
Temporary dipoles will induce dipoles in nearby molecules.
Permanent dipoles can induce dipoles by pushing or pulling electrons across a molecule.
what are hydrogen bonds
Needs a lone pair and hydrogen covalently bonded to F, O or N.
Hydrogen will form a strong permanent dipole-dipole interaction with another oxygen, fluorine or nitrogen atoms.
Forms water, ammonia or hydrogen fluoride. When hydrogen is bonded to very electronegative elements, it forms a strong partial – charge.
bond polarity
Polar molecules- distribution of electrons between covalently bonded molecules aren’t even. Has an overall charge.
Non-polar molecule- distribution of electrons between covalently bonded molecules is even. Has no overall charge
what are covalent bonds
Non-metals bond with each other by sharing valence electrons to form a covalent bond.
By sharing electrons, the atoms acquire a full valence shell and so have a stable noble gas configuration.
what is single covalent bonding
electrostatic attraction between a pair of shared valence electrons and the nuclei. Formed by the sharing of 2 electrons adjacent atoms
what are multiple covalent bonding
more than 1 covalent bond formed
what is dative bonding as a form of covalent bonding
occurs when an atom shares a lone pair of electrons to form a covalent bond rather than each element providing one each.
what is a simple molecular lattice
Simple molecules can form lattices with molecules arranged in a repeating pattern.
The lattice is inly held together by weak induced dipole-dipole forces present
