Building single covalent bonds with dots and crosses

4 minAS Level3.7.1

AI-drafted, independently checked · not yet teacher-reviewed

By the end of this lesson

By the end, you can draw and read dot-and-cross diagrams for molecules that share single electron pairs.

Dots and crosses are a counting trick

Draw only the outer-shell electrons. Use dots for one atom and crosses for the other, so you can see where each electron came from.

A shared pair sits between two atom symbols and counts for both atoms. The marks are just a bookkeeping trick: real electrons are not different shapes.

Worked example: Start with water

Draw a dot-and-cross diagram for H₂O.

Have a go first?

Dots and crosses mark which atom supplied each electron in a shared pair.

Count the pairs

Multiple choiceQuestion 1 · Recall

Multiple choiceQuestion 2 · Apply

Answer the 2 questions above to continue.