RAM is the mean mass of an atom relative to 1/12th the mass of an atom of carbon–12.

(RFM or Mr) is the sum of the relative atomic masses of all the atoms in a chemical formula.

Relative formula mass

Combined science

Atomic structure (negligible electron mass)

Developing a model for atoms

Atoms, elements and compounds

Modern periodic table and electron configuration

Using the periodic table: atomic and mass number

Isotopes

Development of the periodic table

In the Structure and Bonding unit, pupils will build on their understanding of atomic structure to explore different types of chemical bonding and how these bonds affect the properties of substances.

In the Atoms, Elements and Compounds unit, pupils learned about the differences between atoms, elements, and compounds, as well as their chemical symbols and formulae.

This unit covers the atomic model, relative atomic mass, isotopes, and the structure of the modern periodic table. It explains how atomic structure influences element positioning, properties, and reactivity. The focus is on identifying trends and using models to develop scientific explanations.

Atomic structure and the periodic table

What does the relative atomic mass (RAM or Ar) compare the mean mass of an atom to?

use the periodic table to find the relative atomic masses of each type of atom

identify the number of each type of atom in the formula

calculate the number of atoms × the relative atomic mass value for each element

add up the total relative atomic masses of all the atoms

Order the following steps to calculate the RFM of a compound correctly. Start withe periodic table.

What is the relative formula mass (RFM or Mr) of water (H₂O)?

Calculate the RFM of carbon dioxide (CO₂)

the RFM of the compound and the RAM of the element

the total number of electrons in the compound

To calculate the percentage by mass of an element in a compound, you need:

What is the percentage by mass of hydrogen in water (H₂O)? Give your answer to four significant figures.

the atomic number represents the number of protons + neutrons

the atomic number represents the number of neutrons

the atomic number represents the number of protons + electrons

the atomic number represents the number of protons

Which statement accurately describes the atomic number of any given element?

True or false: The atomic mass number of an element is listed on the periodic table.

the number of protons in the nucleus of an atom

sum of the number of protons and neutrons in the nucleus of an atom

average mass of an element's isotopes, based on their abundances

Match each term with its correct definition.

Isotopes of the same element have the same atomic number because they contain the same number of protons. However, they have different relative atomic masses due to varying numbers of {{}}.

If an element has an atomic number of 8 and an average atomic mass of 16, which element is it?

The {{}} number is always a whole number because it represents the fixed number of protons in the nucleus of an atom.

Relative formula mass

Lesson outcome