Chemical formulae of compounds - Atoms, elements and compounds - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize (2024)

FAQs

What formulas do you need to know for GCSE Chemistry AQA? ›

The chemical formula for a substance shows how many atoms of each element are present in a molecule, or the proportion of atoms of each element. The formula can be worked out using the valency.

A compound. is a substance that contains two or more elements. that are chemically combined. The elements in a compound are present in fixed proportions.

An element is a substance that is made up of only one kind of atom. The atoms in a particular element are the same as each other, and they are different from the atoms of all other elements. For example, copper and gold are elements.

To get a 9 in GCSE Chemistry, you need to have a strong understanding of the subject, including a wide range of concepts, theories, and practical skills. You also need to be able to apply your knowledge to a variety of different scenarios and questions, and be able to analyze and interpret complex data and information.

Single-atom negative ions end in “-ide”, so binary compounds always have this ending. Polyatomic compounds usually end in “-ate” or “-ite”. FORMULAS: Write the positive ion, with its charge, then the negative ion, with its charge.

The general formula of a hom*ologous series can be used to figure out the molecular formula of a compound with that particular functional group and n carbon atoms. For example the general formula of alcohols is CnH2n+1OH. If there are 3 x C atoms, there will be (2 x 3) + 1 = 7 x H atoms.

In GCSE Chemistry, cracking refers to the process of breaking down large hydrocarbon molecules into smaller ones by heating them in the presence of a catalyst.

Is air a mixture in GCSE? ›

Air is a mixture that contains the elements nitrogen, oxygen and argon, and also the compound carbon dioxide.

For example, water isn't on the periodic table because it is a compound, not an element. Water is made from the element hydrogen bonded to the element oxygen.

The symbol for an atom indicates the element via its usual two-letter symbol, the mass number as a left superscript, the atomic number as a left subscript (sometimes omitted), and the charge as a right superscript.

Water cannot be separated into its constituent elements by physical methods like magnetic separation, winnowing, etc. The property of water is completely different from its constituent elements hydrogen and oxygen. Hence, water is a compound.

Copper is a chemical element with symbol Cu and atomic number 29.

A formulation is a mixture that has been designed to do something useful. It is formed by mixing together several different substances in carefully measured quantities to ensure the product has the required properties.

In the GCSE chemistry exam, you'll be provided with a periodic table, so don't worry too much about learning all the elements by heart. You will however, need to recall information on the reactivity series to predict how metals will react.