The Periodic Table, Metals and Non-metals: notes

Periodic Table and Trends

• Group: A vertical column. Elements in the same group have the same number of outer electrons, so they behave in similar ways.
• Period: A horizontal row. The period number tells you how many electron shells an atom has.
• Metals and non-metals: Metals are on the left and in the middle. Non-metals are on the right.
• Trend across a period: Metallic character falls from left to right, and elements change from metals to non-metals.
• Trend down a group: Atoms get bigger, and their outer electrons are further from the nucleus.

Groups of Elements

• Group I (alkali metals): Soft, shiny metals that react with water to form an alkali and hydrogen. They get more reactive going down the group.
• Group VII (halogens): Non-metals that exist as pairs of atoms. Colour gets darker and melting points rise going down the group. Reactivity falls going down.
• Group 0 (noble gases): Very unreactive, because their outer shell is full. They exist as single atoms.
• Transition metals: Found in the middle of the table. They are hard, have high melting points, form coloured compounds, and often act as catalysts.

Reactivity and Extraction of Metals

• Reactivity series: A list of metals from most to least reactive: potassium, sodium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold.
• Displacement: A more reactive metal pushes a less reactive metal out of its compound.
• Iron: Extracted from haematite in a blast furnace using coke and limestone.
• Aluminium: Extracted by electrolysis of molten aluminium oxide. This uses a lot of electricity.
• Copper and gold: Copper is extracted from its ores and purified. Gold is found uncombined, so it is separated by physical methods.

Rusting, Alloys and Uses

• Rusting: Iron reacts with oxygen and water to form hydrated iron(III) oxide. Both are needed.
• Prevention: Use paint, oil or grease, galvanising (a zinc coating), or a more reactive metal that corrodes in place of the iron.
• Alloy: A mixture of a metal with another element. Steel is iron with carbon. Brass is copper with zinc. Alloys are usually harder than pure metals.

Air, Water, Gases and Fertilisers

• Air composition: About 78% nitrogen, 21% oxygen, 0.9% argon, and 0.04% carbon dioxide.
• Water treatment: Water is passed through screens, settled, filtered, and disinfected with chlorine.
• Tests: Hydrogen gives a squeaky pop with a lighted splint. Oxygen relights a glowing splint. Carbon dioxide turns limewater milky.
• Worked calculation (percentage nitrogen in ammonium nitrate, NH₄NO₃): Mr = (14 × 2) + (1 × 4) + (16 × 3) = 80. Nitrogen mass = 28. Percentage = 28 ÷ 80 × 100 = 35%.

Common slips

• Mixing up groups and periods. Groups are columns, and periods are rows.
• Saying halogen reactivity increases down the group. It decreases.
• Forgetting that rusting needs both oxygen and water.
• Calling steel an element. It is an alloy.