Students will be supplied with a periodic table for the exam and should be…

The idea

This cluster of skills underpins all of GCSE Chemistry: reading the supplied periodic table to name and symbolise elements, converting between names and formulae, and representing reactions as word equations or balanced symbol equations. You must know the first 20 elements by name and symbol, the Group 1 and Group 7 elements, and other specified elements such as Fe, Cu, Zn, Ag and Au. From a formula such as Ca(OH)₂ you name calcium hydroxide; from a symbol equation you identify compounds by their formulae. Word equations name reactants and products, for example hydrochloric acid + sodium hydroxide → sodium chloride + water. Balanced equations use formulae with state symbols where required and conserve atoms of each element.

What earns the marks

• Correctly names and writes symbols for the first 20 elements, Group 1 elements (Li, Na, K, Rb, Cs) and Group 7 elements (F, Cl, Br, I, At), plus other specified elements such as Fe, Cu, Zn, Ag and Au.
• Names compounds from given formulae, including those with brackets and Roman numerals where appropriate, for example FeCl₂ is iron(II) chloride and Ca(OH)₂ is calcium hydroxide.
• Writes word equations that identify all reactants and products by name for the reactions in this specification, including neutralisation, combustion, displacement and precipitation.
• Writes formulae for reactants and products using the periodic table to deduce ions and combining ratios, for example Al³⁺ with O²⁻ gives Al₂O₃.
• Balances symbol equations by adjusting coefficients so that the number of atoms of each element is the same on both sides, and includes state symbols where the question requires them.
• Checks that a balanced equation is consistent with the word equation and with conservation of mass, and that formulae contain correct subscripts and charges.

Common mistakes and how to put them right

• Writing element symbols with incorrect capitalisation, such as co for cobalt instead of Co.

  Put it right: Use one capital letter followed by lower-case letters as shown on the periodic table.

• Balancing by changing subscripts in a formula, for example turning H₂O into H₂O₂ to balance hydrogen.

  Put it right: Change only the large coefficient in front of a formula.

• Omitting state symbols or using them inconsistently when the question asks for them.

  Put it right: Add (s), (l), (g) or (aq) after each formula as appropriate.

Exam tips

• Spend a moment checking every symbol against the periodic table before writing, especially for elements with similar names such as magnesium and manganese.
• When balancing, count atoms element by element and write the counts beside the equation; adjust coefficients and recount until each element matches.
• For word equations, use the exact chemical names from the specification rather than everyday names, and include the correct products for the reaction type.