structure and bonding

Question 1

polar vs non polar

Answer 1

shape, how many polar bonds there are, do the polar bonds cancel out due to symmetry and equal charge?, is the molecule polar or non polar?

Question 2

symmetrical shapes

Answer 2

tetrahedral, linear, trigonal planar

Question 3

bond angles

Answer 3

linear = 180, tetrahedral = 109.5, trigonal planar = 120
trigonal pyramidal = 109.5
bent = 109.5

Question 4

asymmetrical

Answer 4

trigonal pyramidal
bent/v

Question 5

ionic solids

Answer 5

high melting point - strong ionic & intermolecular bonds
can conduct charge in molten = freely moving charged particle not solid as fixed structure
hard = strong ionic and intermolecular bonds holding in a fixed structure
brittle when force is applied as planes of 3D lattice shift so like charges line up and repel
metal + non metal
soluble in polar solvents

Question 6

metallic solid

Answer 6

strong metallic non-directional bonding between metal cations and sea of delocalised electrons
high melting point due to strong metallic non-directional bonding
insoluble - water attractions not strong enough to overcome metallic bonding
sea of delocalised valence electrons = freely moving charged particles - can conduct as they move across the lattice - non directional bonding
malleable and ductile - non-directional bonding metal solid can change shape without breaking as cations move without breaking bonds

Question 7

lewis structure

Answer 7

He = 2
H = 2
Be = 4
B = 6

Question 8

molecular solids

Answer 8

non-metals
strong covalent weak intermolecular vdw
low mp and bp due to weak intermolecular bonds
neutral so it cannot conduct electricity
polar molecules increase mp and bp due to hydrogen bonding
like dissolves in like

Question 9

2D covalent

Answer 9

weak intermolecular
strong intra covalent
layers - slippery
graphite - allotrope - different physical form of the same element
1 delocalised valence electron that can conduct charge = carbon bonds to 3 other in hexagonal layers
covalent bonding = high mp and bp
solubility - insoluble due to strong covalent

Question 10

3D covalent

Answer 10

diamond (C) and SiO2
stable tetrahedral arrangement = hard
breaks under immense pressure hit
bonded to 4 other C or O atoms = cannot conduct due to no freely moving charged particle
insoluble = covalent bonds too strong to be overcome by polar or non polar
covalent bonds too high = requires a lot of energy = high mp and bp

Question 11

enthalpy equations

Answer 11

n=m/M
∆rH = ∆E/n
∆rH = E bonds broken - E bonds formed

Question 12

bonds broken

Answer 12

requires energy to break bonds = endothermic (+)

Question 13

bonds formed

Answer 13

releases energy = exothermic (-)

Question 14

n=m/M

Answer 14

n = moles
M = g per mol

Question 15

∆rH = ∆E/n

Answer 15

∆rH = kJ per mol

Question 16

more energy released by bonds broken is greater than energy used

Answer 16

exo

Question 17

energy needed to form bonds greater than energy released breaking

Answer 17

endo