Dot-and-Cross Diagrams (x) Flashcards

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Look through all the flashcards to see what's on both sides.
Make sure you understand the information on each card. If something's unclear, click the link to the revision notes at the bottom of the page for more details.

2️⃣ Test yourself:

Look at the question or prompt on each card and try to remember the answer before flipping it over.
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3️⃣ Consistently Review and Practice:

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Note: We may include questions that have multiple correct answers. It's useful to remember specific examples to understand these concepts better.

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What is a dot-and-cross diagram used for in chemistry?

It is a drawing that shows outer-shell electrons and how atoms gain, lose or share them when they bond.

In a dot-and-cross diagram, what do the dots and the crosses each represent?

They both represent electrons, but dots show electrons from one atom and crosses show electrons from a different atom.

Why do dot-and-cross diagrams usually show only the outer electron shell of each atom?

Because only the outer-shell (valence) electrons are involved in bonding, so the inner full shells are left out to keep the diagram simple.

How would you draw a dot-and-cross diagram for a molecule with a single covalent bond, such as Cl2?

Draw the outer shells of two chlorine atoms. Put one electron from each atom between them as a shared pair (one dot and one cross). Then add the rest of the outer electrons so each chlorine has eight electrons in its outer shell.

In a covalent dot-and-cross diagram, what does one shared pair of electrons between two atoms show?

It shows a single covalent bond, where the two atoms share that pair of electrons to get full outer shells.

In a dot-and-cross diagram, how is a double covalent bond between two atoms shown?

It is shown as two shared pairs of electrons between the atoms. For example, there are two shared pairs between the carbon and each oxygen in CO2.

In a dot-and-cross diagram for sodium chloride (NaCl), what happens to sodium’s one outer electron?

It is transferred to the chlorine atom. Sodium becomes a Na+ ion with no electrons in its outer shell. Chlorine becomes a Cl- ion with a full outer shell of eight electrons.

Why are ions in ionic dot-and-cross diagrams drawn inside square brackets with a charge sign, such as [Cl]-?

The brackets and charge show that the particle is an ion and give its overall charge after gaining or losing electrons.

In dot-and-cross diagrams, how many electrons in the outer shell usually show a stable, full shell for an atom (except hydrogen)?

Eight outer-shell electrons show a full, stable shell for most atoms in these diagrams.

What is meant by a lone pair of electrons in a dot-and-cross diagram of a molecule like water?

A lone pair is a pair of electrons on one atom that is not shared in a bond, for example the two non-bonding pairs on the oxygen atom in H2O.

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