Structure Flashcards
Name compounds, elements or ions which are tetrahedral.
Methane 109.5
Ammonium ion 109.5
Sulfate ion 109.5
Name compounds, elements or ions which are trigonal planar
Boron trichloride 120
Carbonate ion 120
Nitrate ion 120
Name compounds, elements or ions which are bent
Water 104.5
Sulfur dioxide 120
Name compounds, elements or ions which are trigonal bypyrimidal
Phosphorus pentachloride (in gas phase) 90 & 120
Name compounds, elements or ions which are pyramidal
Ammonia 107
Name compounds, elements or ions which are octahedral
Sulfur hexafluoride 90
Name compounds, elements or ions which are linear + state their bond angle
Carbon dioxide 180
Beryllium chloride 180
Hydrogen Chloride 180
Why is sulfur dioxide bent?
The lone pair and a bonding pair repel more than a bonding pair and a bonding pair
Why is ammonia pyramidal?
There are 3 bonded pairs and one lone pair of electrons. The bonded pairs repel less with each other than the lone pair and the bonded pair which results in a pyramidal shape.
Marking points for why one angle MAY be smaller than the other?
Extra lone pair
Lone pairs repel more
Bonding pairs are pushed closer together
Why are bond angles the angle they are?
to minimise repulsion of electron pairs
equation for working out the number of lone pairs
1/2 x [group number of the element - number of covalent bonds (not including covalently bonded lone pairs bc don’t know what they are!]
go to phrase about repulsions
lone pair-lone pair repulsions are greater than lone pair-bonding pair repulsions which are greater than bonding-bonding pair repulsions
analogous molecules to:
1) CH4
2) NH3
3) H2O
1) CH4 —> SiH4
2) NH3 —> PH3
3) H2O —-> H2S
How many lone pairs does ammonia (NH3) have?
1
How many lone pairs does wat have?
2
How many lone pairs does sulphur dioxide (SO2) have?
1
carbonate and nitrate ions both have…
two single bonds, one double (two snakes, one den)
SO4 2- drawing has…
a wedge
a dash
two double bonds
What to always say about electron repelling? ?????
electrons repel to MINIMISE REPULSION ??????? check tutorial answers
how many degrees does one pair of lone electrons decrease bond angle by?
2.5 degrees
complex shapes
variations of octahedral and trigonal bypyramidal where some bonds are replaced with lone pairs
4 divisions of structures for solids
1) giant ionic
2) giant covalent
2) metallic
3) simple molecular
Giant ionic lattices (two examples and diagram description)
sodium chloride, magnesium oxide
cubic structure with alternating atoms (see chemrevise + practice drawing)
Giant covalent (two examples + description)
diamond (C) - tetrahedral arrangement of C atoms - each C covalently bonded to 4 other C’s
tower -ish drawing
Graphite (C) - planar arrangement of C atoms in layers (hexagons)
C covalently bonded to three other C’s
4th outer electron in each C atom is delocalised. Delocalised electrons present between layers
silicon (IV) oxide / silicon dioxide (same thing) - SiO2
(see chemrevise + practice drawing)
Bonds in giant covalent structures
strong covalent bonds = high melting points
Metallic structure drawing
2D lattice drawing (showing closely packed ions and delocalised e-)
Simple molecular diagram
Eg. regular arrangement of I2 molecules held together by weak london forces
diagram: lots of I-I’s floating about
Ice
draw H2O as though sticking left arm up and right arm out to the right then draw Hydrogen bonds between the oxygen’s two lone pairs and hydrogens branching out to the left (these hydrogens are attached to the rest of two different water molecules)
-tetrahedral arrangement
-molecules held further apart
(see chemrevise)
Properties of diamond
- cannot conduct electricity because all four electrons per atom are involved in covalent bonds
- localised electrons, cannot move
Properties of graphite
- giant covalent
- can conduct electricity because one electron per carbon is delocalised and free to move along layers
BUT doesn’t conduct electricity BETWEEN layers because the energy gap between them is too large for an easy electron transfer
Graphene
- a single one-atom-thick layer of graphite (3 covalent bonds per C atom and a 4th electron per atom which is delocalised).
- thin, nearly transparent sheet
- high tensile strength due to strong covalent bonds
- can conduct electricity because one electron is free and delocalised
C60 - Buckminster Fullerene
- hexagons and pentagons
- red + soluble in organic liquids
Carbon Nanotubes
- used in drug delivery
- tubular structures made from carbon hexagons
- can conduct electricity along tube because one electron per carbon is delocalised and free
solid to gas
sublimation
Why is graphite used as a solid lubricant?
layer slide over each other easily
due to weak forces between the layers
NO3 - is an example of a what covalent bond
dative covalent
One double bond
two single bonds, one drawn showing an arrow to represent dative
tetrahedral bond angle
109.5
plosive tet and NINE.5
trigonal planar bond angle
120
360/3 = planar = 120
bond angle definition
geometric angle between two adjacent bonds
what is the degree of the C-C-C bond angle in diamond?
109.5
Diamond one word shape
TETRAHEDRAL
Graphite one word shape
HEXAGONAL
Buckminster fullerene two word shape
HEXAGONS AND PENTAGONS
Ice one word shape
TETRAHEDRAL (internet say hexagonal as well)
carbon nanotubes one word shape
HEXAGONS
Go to phrase about bonding pairs only
BONDING PAIRS ARE PUSHED CLOSER TOGETHER
How many lone pairs does the wired anomaly shape SF4 have?
one
