3.1.3 Bonding Flashcards
Ionic bonding
Involves electrostatic attraction between oppositely charged ions in a lattice
Sulfate ion
SO₄²-
Hydroxide ion
OH¯
Nitrate ion
NO₃⁻
Carbonate ion
CO₃²⁻
Ammonium ion
NH₄+
Metallic bonding
Involves attraction between delocalised electrons and positive ions arranged in a lattice.
4 types of crystal structure + examples
Ionic - NaCl
Metallic - Mg
Macromolecular (giant covalent) - Diamond/Graphite
Molecular - Iodine/Water
Ionic melting point
High as the electrostatic forces of attraction between the positive and negative ion requires a lot of energy to be overcome
Ionic conductivity
Only when molten or in solution as they are free to move and carry a flow of charge
Are ionic compounds brittle
Yes as when the layers of alternating charges are distorted, like charges repel, breaking the compound
Metal boiling point
Very high, as bond between positive metal ion and delocalised electrons is very taring and requires a lot of energy to overcome
Metals as conductors
Yes as sea of delocalised electrons is free to carry charge
Are metals brittle or malleable
Malleable as layers of positive ions are able to slide over each other. sea of delocalised electrons prevent fragmentation as they can move around the lattice
Simple molecular bonding
Covalently bonded molecules
Held together with weak VDWs
Low boiling point as VDWs easy to break
(exception water as it has hydrogen bonding)
Macromolecular
Many covalent bonds
Very high melting point as lots of energy is required to break covalent bonds
Rigid
Graphite structure
Each carbon is bonded to 3 others in a sheet
One electron per carbon is free to move around
So can conduct electricity
Sheets of carbon can move over each other easily
Electron repulsion (most to least)
Lone pair - Lone pair
Lone pair - Bonding pair
Bonding Pair - Bonding pair
Linear
Bonding pairs: 2
Lone pairs: (3)
Bond angle: 180 (120)
V-shaped
Bonding pairs: 2
Lone pairs: 2
Bond angle: 104.5
Trigonal planar
Bonding pairs: 3
Lone pairs: 0
Bond angle: 120
Triangular Pyramidal
Bonding pairs: 3
Lone pairs: 1
Bond angle: 107
Tetrahedral
Bonding pairs: 4
Lone pairs: 109.5
Bond angle:
Trigonal bipyramidal
Bonding pairs: 5
Lone pairs: 0
Bond angle: 90 &120
Octahedral
Bonding pairs: 6
Lone pairs: 0
Bond angle: 90
Electronegativity
The power of an atom to attract the pair of electrons in a covalent bond. Increases a long a period, decreases down the group.
Permanent dipole
when the two bonded atoms have a large enough difference in electronegativity, the more electronegative atom draws more of the negative charge towards itself. This is a polar molecule. Symmetrical molecules are not polar.
How do induced dipoles arise
Electrons move randomly through the atom, so at any point there may be more on one side than other
This temporary dipole can induce an opposite dipole in a neighbouring atom
This induced dipole can then induce further dipoles in other nearby particles.
Overall effect is net attraction between molecules
Van der Waals
Weak IMF acting as an induced dipole between molecules. The more points of contact, the more VDWs so the higher the melting point. So branched chains usually have lower boiling points as they can line up/pack as closely.
Hydrogen bond
Strongest IMF, acts between hydrogen and either N, O or F. The lone pair on these atoms forms a H bond with the Hydrogen, shown by a dotted line. these molecules have higher b.ps.
R - O: - - - - - - H
