Page 29 - ACE YR IGCSE A TOP APPROACH TO CHEM

(c) (i) Nitrogen has a smaller M . [1]
r
M = Relative molecular mass / Relative 2 Atoms, Elements and Compounds
r
formula mass
Relative molecular mass of N = 14 + 14 = 28 Part 1: Multiple-choice Questions
2
Relative molecular mass of Cl = 35.5 + 35.5 = 71
2 1 B
Nitrogen molecules / particles move faster Valence electrons are the electrons in the outer shell
(than chlorine molecules). [1] of an atom. To make this atom an ion, it needs to gain
Note: Word of comparison must be used. 1 electron to form a negative ion, to achieve a stable
(ii) Molecules / particles move faster / have electron arrangement. Therefore, the ion has 8 valence
more energy. [1] electrons in the outer shell.
At higher temperatures, particles have more 2 C
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kinetic energy to move faster. Protons and neutrons are located in the nucleus and
8 (a) 80°C [1] electrons are located outside the nucleus.
(b) 3 C
There is only 1 electron in the outer shell. To achieve a
Solid Liquid stable arrangement, there must be 8 electrons in the

Arrangement Regular Irregular [1] outer shell.
4 B
Movement Vibrate / Moving / [1] Nucleon number is the total number of protons and
fixed slide past neutrons in the nucleus.
position each other
5 D
Note: Comparison must be made. 1 mark is given The elements are arranged in order of increasing proton
for each comparison. number.
(c) There is no horizontal line. [1] 6 B
In a pure substance, the melting and boiling points There are 3 electrons in the outer shell. Therefore,
should show a horizontal line. it should be located in Group III. From the electronic
9 (a) Any two from: [2] structure, there are 3 shells / orbits, it tells that the
element is located in Period 3 of the Periodic Table.
• Particles move randomly in all directions
• collide 7 A
• move from a region of higher concentration The last number in the electronic configuration indicates
to a region of lower concentration the number of electrons in the outer shell. All Group II
elements have 2 electrons in their outer shell.
(b) C [1]
Ethylamine has a lower M r [1] 8 D
M = Relative molecular mass / Relative formula A compound is a substance that contains more than 1
r
mass element chemically bonded together.
A mixture contains more than 1 element / compound
Relative molecular mass of CH CH NH = 45
3
2
2
Relative molecular mass of HBr = 81 that is mixed.
An element consists of only 1 type of atom.
moves faster. [1] 9 A
Note: Word of comparison must be used.
R is a macromolecule. Particles are bonded by covalent
10 (a) Particles move closer together [1] bonds. It has the highest melting point among all. It
in a smaller space [1] has no mobile electrons, therefore it cannot conduct
collide with the walls more often. [1] electricity.
S is a lattice ionic compound. Particles are bonded by
(b) Particles move in all directions / randomly in ionic bonds. It has a high melting point but lower than
both liquid and gas. [1] macromolecules.
No bonds / very weak forces between particles T is a lattice metal. Particles are bonded by metallic
in gas. [1] bonds.
Gas molecules move apart to fill up the entire U is a simple covalent compound. Particles are bonded
volume. [1] by covalent bonds.
or 10 B
There are bonds / forces between particles in Nitrogen has 5 valence electrons. Hydrogen has 1
liquid. [1] valence electron. 3 hydrogen atoms each share their 1
Molecules cannot move apart, so the volume is electron with 3 individual electrons of nitrogen to form 3
fixed. [1] single bonds. Two more paired electrons in nitrogen are
stable.

Answers 141

Answers.indd 141 3/4/22 3:54 PM