Bonding Flashcards
Ionic Bond
Electrostatic attraction between oppositely charged ions.
Melting point for ionic compounds
High - strong electrostatic attraction between oppositely charged ions
Ionic bonding is stronger when…
Ions are smaller and/or have higher charges. (A higher charge density)
Covalent Bond
Shared pair of electrons
Dative covalent bond
When the shared pair of electrons both come from one of the bonding atoms. Also called co-ordinate bonding.
Metallic bonding
electrostatic force of attraction between cations and a sea of delocalised electrons
Factors that affect strength of metallic bond
Number of protons (more = stronger), number of delocalised electrons (more = stronger), size of ion (smaller = stronger)
4 crystal structures are…
ionic, simple molecular, macromolecular and metallic
conductivity of ionic compounds
poor when solid - ions can’t move. Higher when molten or dissolved - ions free to move
boiling points of molecular compounds
low - weak intermolecular forces between molecules (Van der Waals)
melting point of macromolecular compounds
high - many strong covalent bonds to break
melting point of metallic substances
high - strong electrostatic forces of attraction between cations and delocalised electrons
Conductivity of molecular substances
Poor - no charged particles
Conductivity of macromolecular
Diamond and silica - poor. Not electrons or ions.
Graphite - good as delocalised electrons able to move between layers
Conductivity of metals
Good - delocalised electrons able to move
Shape of molecule with 2 bp, 0 lp
linear 180 angles
Shape of molecule with 3 bp, 0 lp
trigonal planar, 120 angles
Shape of molecule with 4 bp, 0 lp
tetrahedral, 109.5 angles
Shape of molecule with 3 bp, 1 lp
trigonal pyramidal, 107 angles
Shape of molecule with 2 bp, 2 lp
V shape or bent. 104.5 angles
Shape of molecule with 5 bp, 0 lp
trigonal bypyramidal, 120 and 90 angles
Shape of molecule with 5 bp, 1 lp
See-saw
Shape of molecule with 6 bp, 0 lp
Octahedral 90 angles
How to explain shape
- State number of bonding pairs and lone pairs.
- State that electron pairs repel to get as far apart as possible
3a. If no lone pairs state that electron pairs repel equally
3b. If there are lone pairs state that lone pairs repel more than bonding pairs - State shape and bond angle
Shape of molecule with 4 bp, 2 lp
Square planar 90 angles
Shape of molecule with 5 bp, 1 lp
Square based pyramid
How to calculate number of electron pairs
Group of central atom + number of electrons from bonding atoms +/- electrons from charge = total number of electrons. Divide by 2 = number of pairs. Work out whether they are bonding or lone pairs
Shape CO2
linear 180 angles
Shape CS2
linear 180 angles
Shape HCN
linear 180 angles
Shape BeF2
linear 180 angles