HSC Chemistry

Physical and Chemical Properties: IUPAC Nomenclature and Periodic Table Trends

Published 2026-09-28 · Updated 2026-09-28

Many students lose marks in the HSC examination not because they misunderstand chemistry, but because they mix up physical and chemical properties, or they name compounds incorrectly. HSC markers award marks for precise language, and a compound named without the correct IUPAC suffix, or a property placed in the wrong category, will cost you. This guide covers exactly what you need to know for the Properties and Structure of Matter module.

What the syllabus asks

For this concept you need to be able to:

• Distinguish physical properties from chemical properties, with examples of each.
• Apply IUPAC nomenclature to name inorganic substances, including binary ionic compounds, transition metal compounds, polyatomic ions, and common acids.
• Use the position of an element in the periodic table to predict its physical and chemical properties.

The idea, explained

Physical vs chemical properties

A physical property is one you can observe or measure without changing the chemical identity of the substance. Examples include colour, density, melting point, boiling point, solubility, electrical conductivity, malleability, and ductility. Density is calculated using the formula:

density = mass / volume

Common units are g/cm³, g/mL, or kg/m³.

A chemical property describes how a substance behaves during a chemical reaction, where its identity does change. Examples include flammability, reactivity with oxygen or acids, toxicity, and corrosiveness.

The key question to ask yourself: does observing this property require a chemical reaction? If yes, it is a chemical property.

IUPAC nomenclature for inorganic substances

IUPAC names follow consistent rules so that every chemist, anywhere in the world, can identify a substance from its name alone.

Binary ionic compounds (a metal and a non-metal): write the metal name first, then the non-metal with an -ide suffix. For example, sodium and chlorine form sodium chloride; magnesium and oxygen form magnesium oxide.

Transition metals with variable charges: because many transition metals can form more than one type of ion, Roman numerals are placed in parentheses immediately after the metal name to indicate the charge. Iron forming a 2+ ion gives iron(II) chloride; iron forming a 3+ ion gives iron(III) chloride.

Polyatomic anions: some negative ions contain more than one element. You need to know these by name and formula:

• Sulfate: SO4²⁻
• Nitrate: NO3⁻
• Carbonate: CO3²⁻
• Phosphate: PO4³⁻
• Hydroxide: OH⁻

When these appear in a compound, the anion name replaces the -ide ending. For example, sodium and sulfate form sodium sulfate.

Common acids: hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (HNO3) are the three you are expected to know.

Using the periodic table to predict properties

The periodic table arranges elements by increasing atomic number, and an element's position tells you a great deal about its properties before you ever measure anything.

Physical property trends by region:

• Metals (left side and d-block) are solids at room temperature, lustrous, malleable, ductile, and good conductors of heat and electricity.
• Non-metals (upper right, p-block) are often gases or brittle solids, poor conductors, with low melting and boiling points.
• Metalloids (along the staircase boundary: B, Si, Ge, As, Sb, Te) have intermediate properties and act as semiconductors.
• Melting and boiling points increase across a period from group 1 to group 14, then drop sharply for groups 15 to 18.
• Melting and boiling points generally decrease down a group for metals, because larger atoms form weaker metallic bonds.

Chemical property trends:

• Valency follows group number: group 1 gives +1, group 2 gives +2, and p-block elements give +3, ±4, −3, −2, or −1, while noble gases are 0. D-block (transition) metals have variable valency.
• Elements in the same group share the same common valency and react similarly. All group 1 metals, for instance, react with water to produce a metal hydroxide and hydrogen gas.
• Metal reactivity increases down a group and from right to left across a period, because ionisation energy decreases in those directions.
• Non-metal reactivity increases up a group and from left to right across a period, because electronegativity increases in those directions.
• Metallic character increases toward the lower-left of the periodic table; non-metallic character increases toward the upper-right.
• Atomic radius increases toward the lower-left; ionisation energy and electronegativity increase toward the upper-right.

In short, knowing an element's group, period, and block allows you to predict its physical state, conductivity, melting point, valency, and reactivity without any direct measurement.

What the exam asks

HSC examination questions on this concept commonly ask you to:

• Classify a given property as physical or chemical and justify your answer.
• Write the correct IUPAC name for an ionic compound, including Roman numerals where the metal has variable valency.
• Use periodic table position to predict and compare properties of two elements, such as which has a higher melting point or greater reactivity.

When justifying a classification, always link back to whether the chemical identity changes. When naming compounds, always check whether the metal is a transition metal before deciding if a Roman numeral is needed.

Common mistakes

• Confusing toxicity with a physical property. Toxicity describes how a substance reacts with biological systems, so it is a chemical property, not a physical one.
• Forgetting Roman numerals for transition metals. Writing "iron chloride" instead of "iron(II) chloride" or "iron(III) chloride" is incomplete and will not receive full marks from HSC markers.
• Using -ide for polyatomic anions. Sodium sulfate is not "sodium sulfide". The -ide suffix is reserved for single-element anions; polyatomic anions keep their own names.
• Reversing reactivity trends. Students often state that metals become less reactive down a group. In fact, metal reactivity increases down a group as ionisation energy decreases.
• Mixing up atomic radius and ionisation energy trends. Both increase as you move across the periodic table, but in opposite directions: atomic radius increases toward the lower-left, while ionisation energy increases toward the upper-right.

If you want structured practice on all of these ideas, Avocado's AI-native tutoring service has lessons built specifically for the NSW HSC syllabus. Start with the Physical and Chemical Properties lesson to test your understanding and get instant feedback on your answers.