Coaching Centre
Module 1 review
Review of Module 1 Properties and Structure of Matter: summary table, how the ideas connect, a worked exam-style problem that links atomic structure to bonding and properties, key terms and formulas, and a mixed HSC-style test.
Module 1 tells one story in four parts. Matter is made of particles; what those particles are, and how their electrons are arranged, decides how they bond; how they bond decides the structure; and the structure decides the properties you can see and measure. Exam questions reward students who can move along that chain in either direction.
How the ideas connect
| Lesson | Big idea | You must be able to |
|---|---|---|
| 1A Matter | Mixtures keep their components' properties; pure substances have fixed composition | Classify; choose separation techniques by property; calculate % composition by gravimetric analysis |
| 1B Atoms | Z defines the element; isotopes differ in N | Count p, n, e in atoms and ions; calculate Ar and abundances |
| 1C Nuclei | Stability depends on N/Z | Predict α, β⁻, β⁺; balance nuclear equations; half-life |
| 1D Electrons | Subshells s, p, d, f fill by energy | Write spdf and orbital box configurations, including ions, Cr and Cu |
| 1E Spectra | Quantised levels give line spectra | Use E = hc/λ; explain flame tests; compare Bohr and Schrödinger |
| 1F Trends | Effective nuclear charge and distance | Explain radius, IE, EN, reactivity trends; read successive IEs |
| 1G Ionic, metallic | Bonding is electrostatic | Draw ionic dot diagrams; write formulae and names; explain properties |
| 1H Covalent | Shared pairs; domains repel | Draw Lewis structures; predict shape, angle and polarity |
| 1I Forces, networks, allotropes | IMFs decide molecular properties | Identify IMFs; explain bp trends and anomalies; compare allotropes and structure types |
Putting it together
Element X has the configuration 1s² 2s² 2p⁶ 3s² 3p⁴ and element Y has 1s² 2s² 2p⁶ 3s¹. (a) Identify X and Y and their positions. (b) Predict the formula and bond type of the compound they form. (c) Explain which has the larger atomic radius and higher first IE. (d) Predict two properties of the compound.
(a) X has 16 electrons: sulfur, period 3, group 16 (6 valence electrons). Y has 11: sodium, period 3, group 1.
(b) Na loses 1 electron (Na⁺); S gains 2 (S²⁻). Neutral ratio 2 : 1, Na₂S. ΔEN = 2.58 − 0.93 = 1.65, close to the ionic boundary, and a metal with a non-metal: ionic.
(c) Both are in period 3. S has 16 protons against Na's 11, with the same number of inner shells, so its effective nuclear charge is larger: S has the smaller radius and the higher first IE (1000 vs 496 kJ mol⁻¹). Na has the larger radius.
(d) As an ionic lattice, Na₂S has a high melting point (1176 °C), is brittle, and conducts electricity when molten or dissolved but not as a solid.
Key terms and formulas
| Term | Meaning |
|---|---|
| Percentage composition | mass of component ÷ mass of sample × 100 |
| Relative atomic mass | $A_r = \sum(\text{isotopic mass} \times \%)/100$, relative to ¹²C = 12 |
| Isotopes | Same Z, different N |
| Half-life | $m = m_0(\tfrac{1}{2})^{t/t_{1/2}}$ |
| Photon energy | $E = hf = hc/\lambda$; h = 6.626 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m s⁻¹ |
| Orbital | Region of high probability of finding an electron; holds 2 electrons of opposite spin |
| First ionisation energy | Energy to remove one mole of electrons from one mole of gaseous atoms |
| Electronegativity | Ability of an atom to attract shared electrons in a covalent bond |
| Electron domain | A lone pair or a bond (single, double or triple) around a central atom |
| Hydrogen bond | Attraction between H bonded to N, O or F and a lone pair on N, O or F of another molecule |
| Allotropes | Different structural forms of the same element in the same state |
Test yourself
Which pair of substances could be separated by a separating funnel?
Hexane and water are immiscible liquids of different density.
Gallium has isotopes ⁶⁹Ga (68.93, 60.1%) and ⁷¹Ga (70.92, 39.9%). Its Ar is
(68.93 × 60.1 + 70.92 × 39.9) ÷ 100 = 69.72.
Which nuclear equation is balanced?
60 = 60 + 0 and 27 = 28 − 1. The others have wrong Z values.
The electron configuration of Cr³⁺ is
Cr is [Ar] 4s¹ 3d⁵; remove 4s¹ then two 3d electrons.
Which element has the highest first ionisation energy?
N (1402) is higher than O (1314) because O has a paired 2p electron; Li and Na are much lower.
Which molecule has a trigonal planar shape?
SO₃ has three domains and no lone pair on S. NH₃ and PCl₃ are pyramidal.
Propan-1-ol (C₃H₇OH, 60 g mol⁻¹) boils at 97 °C, while butane (C₄H₁₀, 58 g mol⁻¹) boils at −1 °C. The main reason is
Similar masses and electron numbers, but only the alcohol has O–H groups.
Solid X conducts electricity, has a melting point above 3500 °C, and is soft and flaky. X is
Only graphite combines conductivity, very high mp and softness.
Label the key features of the hydride boiling point graph.
Classify each substance by its structure.
Atoms of the same element always have the same number of . Down a group, atomic radius increases because each element has an extra . The most electronegative element is . A molecule with polar bonds can be non-polar if its shape is . Melting a covalent network solid requires breaking bonds.
Silicon (Z = 14) and chlorine (Z = 17) are both in period 3. Silicon is a grey solid that melts at 1414 °C and is a semiconductor; chlorine is a green gas that boils at −34 °C. They react to form silicon tetrachloride, SiCl₄, a liquid that boils at 58 °C. (a) Write the electron configurations of Si and Cl and explain which has the higher first ionisation energy. (b) Explain the difference between the melting point of silicon and the boiling point of chlorine in terms of structure and bonding. (c) Predict the shape and polarity of SiCl₄ and explain why it is a liquid at room temperature.
(a) Si: 1s² 2s² 2p⁶ 3s² 3p². Cl: 1s² 2s² 2p⁶ 3s² 3p⁵. Both have their outer electrons in the third shell with the same 10 inner electrons shielding them, but Cl has 17 protons against 14. Its larger effective nuclear charge pulls the outer electrons closer and holds them more tightly, so Cl has the higher first IE (1251 vs 787 kJ mol⁻¹).
(b) Silicon is a covalent network solid: every Si atom is covalently bonded to four others throughout the crystal. Melting requires breaking many strong covalent bonds, so its melting point is very high. Chlorine is covalent molecular: each Cl₂ molecule has a strong covalent bond, but the molecules are held to each other only by weak dispersion forces. Little energy is needed to separate the molecules, so chlorine boils at −34 °C.
(c) SiCl₄ has four bonding domains and no lone pairs on Si, so it is tetrahedral with 109.5° angles. The Si–Cl bonds are polar (ΔEN 1.26), but four identical dipoles arranged symmetrically cancel, so the molecule is non-polar. Only dispersion forces act between its molecules, but each molecule has 82 electrons, so these forces are strong enough to keep SiCl₄ liquid at room temperature.