Atoms, elements and compounds: use the names and symbols of the first 20 elements in the periodic table, the elements in Groups 1 and 7, and other elements in this specification

The idea

This skill means you can move confidently between an element's name and its chemical symbol. You need the first 20 elements, from hydrogen (H) to calcium (Ca), plus Group 1 elements such as sodium (Na) and potassium (K), and Group 7 elements such as chlorine (Cl) and bromine (Br). You also need other elements named in the specification, for example iron (Fe), copper (Cu) and zinc (Zn). Learn symbols with their exact capitalisation: the first letter is always a capital and any second letter is always lower case, so Co is cobalt but CO would mean carbon monoxide. A useful method is to cover the name, write the symbol from memory, then check the periodic table. Practise both directions, because an exam may give a name and ask for the symbol, or give a symbol and ask for the name.

What earns the marks

• Correctly pairs each of the first 20 elements with its symbol, for example potassium with K and calcium with Ca.
• Correctly pairs Group 1 elements with symbols, for example lithium with Li, sodium with Na and potassium with K.
• Correctly pairs Group 7 elements with symbols, for example fluorine with F, chlorine with Cl and bromine with Br.
• Correctly names and gives symbols for other specification elements such as iron (Fe), copper (Cu) and zinc (Zn).
• Uses correct capitalisation, including two-letter symbols such as Mg, Cl and Ca, and distinguishes Co (cobalt) from CO (carbon monoxide).
• Responds accurately in either direction, converting a name to a symbol or a symbol to a name.

Common mistakes and how to put them right

• Writing symbols with incorrect capitalisation, such as CL for chlorine or na for sodium.

  Put it right: Cl and Na, because the first letter is a capital and the second is lower case.

• Confusing elements with similar names or symbols, such as magnesium (Mg) and manganese (Mn).

  Put it right: Link each name to its exact symbol and position in the periodic table.

• Treating a two-letter symbol as two separate elements, for example reading NaCl as sodium and carbon and lithium.

  Put it right: Recognise Na as sodium and Cl as chlorine.

• Assuming every element named in a question is in the first 20.

  Put it right: Learn the additional specification elements, including iron, copper and zinc.

Exam tips

• Make a two-column list of names and symbols and test yourself in both directions until you can recall them without the periodic table.
• When a question gives a formula, identify each symbol first and then write the element name, checking capitalisation carefully.
• If you cannot recall a symbol, use the periodic table provided in the exam rather than leaving the answer blank.
• Write symbols clearly so that a lower-case l is not mistaken for a capital I or the digit 1.