shapes of molecules and ions

Question 1

predict with reasons the bond angle in ammonia

Answer 1

e pairs repel, must get as far apart as possible, lp repel more than bp, so bp get closer together, ammonia has 1lp so bond angle is reduced to 107

Question 2

shape and bond angle of water

Answer 2

non-linear, 104.5, 2lp 2bp

Question 3

shape and bond angle of ammonia

Answer 3

trigonal pyramidal, 107, 1lp 3bp

Question 4

shape and bond angle of methane

Answer 4

tetrahedral, 109.5, 0lp 4bp

Question 5

model mark scheme

Answer 5

name, bond angle, n bp lp where relevant, lp>bp so bp closer/ bp repel equally (dep on q)

Question 6

give n example of a simple covalent molecule which has all bond angles equal to 90’

Answer 6

.

Question 7

By reference to all the atoms involved explain, in terms of electrons, how Na2S is formed from its atoms.

Answer 7

electron transfer from Na to S

1 e from each of 2 Na atoms

Question 8

Predict the shape of the AlH4- ion. Explain why it has this shape.

Answer 8

tetrahedral, =repulsion, bw 4 bps

Question 9

A bond in AlH4- can be represented by H → Al

Answer 9

diative/ coordinate
lone pair
donated from H- to Al

Question 10

Sodium reacts with ammonia to form the compound NaNH2 which contains the NH2– ion.
Draw the shape of the NH2– ion, including any lone pairs of electrons.
Name the shape made by the three atoms in the NH2– ion.

Answer 10

bent
labelled atoms
lone pairs

bent

Question 11

ICl3

Answer 11

3bp, 2lp, trigonal pyramidal

Question 12

NO2-

Answer 12

2bp( double bonds), 1lp, bent

Question 13

XeF2

Answer 13

2bp, 3lp bent

Question 14

H30+

Answer 14

3bp, 1lp, trig pry 107

Question 15

ClF3

Answer 15

3bp, 2lp, trig pry

Question 16

XeF4

Answer 16

4bp, 2lp, sq planar 90’/ sq base pyr 85

Question 17

describe and draw the bonding in CS2

Answer 17

covalent,

Question 18

every lone pair reduces the bond angle by

Answer 18

2.5

Question 19

what does EPR enable use to predict

Answer 19

arragement of e pairs around a central atom of unfamiliar molecules and ions

Question 20

bond angle and shape of an ammonium ion

Answer 20

109.5, tetrahedral

Question 21

carbonate, nitrate ions

Answer 21

both have 3 regions of e density so trig planar 120

Question 22

sulfate ion

Answer 22

have 4 centres of e density around central atom so tet 109.5

Question 23

octrahedral shape

Answer 23

6bp, 90

Question 24

which e pairs repel more strongly

Answer 24

lps

Question 25

predict with reasons bond angles in F3BNH3

Answer 25

all 109.5, boron and nitrgoen now have four bonded electrons around boron and nitrogen