Eduqas GCSE Chemistry 4 The Periodic Table and Properties of Elements Exam Questions

About Eduqas GCSE Chemistry 4 The Periodic Table and Properties of Elements

This Eduqas GCSE Chemistry topic explains how the modern Periodic Table is arranged and uses it to predict properties. You study the noble gases, the alkali metals and the halogens, including their trends and reactions, and compare transition metals with Group 1. The topic also covers chemical analysis: flame tests, instrumental methods such as flame emission spectroscopy, tests for halide ions using silver nitrate, and tests for common gases. Examiners frequently ask you to explain trends in reactivity using electrons and shells, write equations for Group 1 and Group 7 reactions, and identify unknown substances from test results (SP4).

What you need to know

• Arrangement Elements are arranged in order of atomic number. Groups (columns) have the same number of outer electrons and similar reactions; periods (rows) show the number of shells. Metals are on the left, non-metals on the right.
• Group 1 Alkali metals are soft, have low densities and react with water to form an alkaline hydroxide and hydrogen, for example 2Na + 2H2O → 2NaOH + H2. Reactivity increases down the group because the outer electron is further from the nucleus and more shielded, so it is lost more easily.
• Group 7 Halogens exist as diatomic molecules. Down the group, colour darkens, melting and boiling points increase and reactivity decreases, because it is harder to gain an electron. A more reactive halogen displaces a less reactive halide from solution, for example chlorine displaces bromide.
• Group 0 and transition metals Noble gases are unreactive because they have full outer shells; boiling points increase down the group. Transition metals are harder, denser and have higher melting points than Group 1 metals, form coloured compounds, have ions with different charges and are useful catalysts.
• Flame tests and instruments Lithium crimson, sodium yellow, potassium lilac, calcium orange-red, copper green. Instrumental methods such as flame emission spectroscopy are faster, more accurate and more sensitive, and can measure concentration.
• Tests for ions and gases Add dilute nitric acid then silver nitrate: chloride gives a white precipitate, bromide cream, iodide yellow. Hydrogen gives a squeaky pop with a lit splint, oxygen relights a glowing splint, carbon dioxide turns limewater milky and chlorine bleaches damp litmus paper. SP4: identify unknown substances using these tests.

Common mistakes in 4 The Periodic Table and Properties of Elements

• Explaining Group 1 reactivity by saying the atoms have fewer electrons. Explain that the outer electron is further from the nucleus with more shielding, so less attraction and it is lost more easily.
• Applying the Group 1 trend to Group 7. Halogen reactivity decreases down the group because it becomes harder to attract and gain an electron.
• Writing halogens as single atoms in equations. They are diatomic: Cl2, Br2, I2.
• Forgetting to add nitric acid before silver nitrate. The acid removes carbonate ions that would also give a precipitate.
• Mixing up the gas tests for hydrogen and oxygen. Hydrogen: lit splint, squeaky pop. Oxygen: glowing splint relights.

Try three 4 The Periodic Table and Properties of Elements exam-style questions