Author: nashton
Company: RM plc

F321 module 2 Practice 3:
1.	(i)	
	
	positive ions 	electrons  (must be labelled)
If Mg^2+ shown then must be correct: Mg^+ not worthy	2
(ii)	electrons move 	1
[3]

2.	(i)	Oxidation state goes from 0 in O_2 
→ −2 in MgO 	2
(ii)	

or with Mg full shell.
correct dot and cross; correct charges	2
[4]

3.	(i)	mark vertically:
	H_2O	NH_3
	2	3
	2	1	2
		
3D Diagram required or diagram with name
(ii)	labelled bond angle required
NH_3        pyramidal molecule shown 	107 ° (106-108°)
SO_2        non-linear molecule shown        110 – 130 ° 	4
[6]

4.	(i)	oxygen/ nitrogen is more electronegative/
molecule has atoms with different electronegativities
/oxygen/more electronegative atom … attracts bonded
electron pair more 	1
(ii)	H bonding from N of 1 NH_3 molecule to H of another NH_3
molecule with a H^δ+ shown and a N^δ–  shown
with lone pair involved in bond
2nd mark is available from water molecule(s)	2
[3]

5.	ice is less dense than water
hydrogen bonds hold H_2O molecules apart in ice /
hydrogen bonds cause an open lattice structure	2
[2]

6.	(a)	Energy change when each atom in 1 mole
of gaseous atoms
loses an electron  (to form 1 mole of gaseous 1+ ions).	3

(b)	From Li → N, ionisation energy increases
number of protons/nuclear charge increases
nuclear attraction increases / shell drawn in by increased
nuclear charge/ atomic radius decreases
across period, electrons added to same shell
Not same subshell
From Be → B, ionisation energy decreases
for B, electron is removed from a p sub-shell/p
orbital/different sub-shell
which has a higher energy	7
watch for distinction between nuclear attraction and
nuclear charge in candidates’ scripts.
Also watch for confusion between shell and subshell.
Al
Sharp rise in successive ionisation energy between 3rd and
4th IE
marking a change to a new or different shell / there are 3
electrons in the outer shell	3
mention of ‘orbital’ or ‘sub-shell cancels ‘shell mark’ Each marking point for Al is independent
	QoWC:	links together two pieces of information
	correctly within two of the sections below:
	1. General trend across period
	2. Be to B
	Successive ionisation energies
[13]

7.	(i)	107°  (accept any angle in the range 108° → 91°)	1
(ii)	electron pairs repel electron pairs/bonds go as far apart as possible
lone pairs repel more 	2
[3]

8.	(i)	Ca^+(g) → Ca^2+(g) + e^−
Equation with correct charges and 1 electron lost 
state symbols 
‘−’ not required on ‘e’	2
(ii)	same number of protons or same nuclear charge attracting
less electrons/
electron removed from an ion/
less electron-electron repulsion (not less shielding)/
ion is smaller	1
(iii)	atomic radii of Sr > atomic radii of Ca/
Sr has electrons in shell further from nucleus than Ca/
Sr has electrons in a higher energy level/
Sr has more shells 
Therefore less attraction 
Sr has more shielding than Ca 
(‘more’ is essential)	3
	increased nuclear charge is outweighed / despite increased nuclear
charge …..by at least one of the factors above 
[6]

9.	attraction between oppositely charged ions/
oppositely charged atoms 	1
 
	For CaO: correct dot and cross ; correct charges 
For CO_2: correct dot and cross 	3
 
	1s^22s^22p^63s^23p^6 	1
[5]

10.	(i)	dative covalent, bonded pair comes from same atom/	1
electron pair is donated from one atom/
both electrons are from the same atom 
(ii)	Ca(NO_3)_2 → CaO + 2NO_2 + ½O_2 
or double equation with 2/2/4/1	1
[2]

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