All elements occur naturally on Earth.

• True

• False

The chemical formula of a phosphorus molecule is P₂.

• True

• False

Semi-metals can conduct electricity when they are mixed with a small amount of impurities.

• True

• False

The nucleus contains tightly packed protons and neutrons.

• True

• False

All elements are made up of molecules.

• True

• False

The chemical symbol of gold is Au.

• True

• False

The melting point of sodium is below 100 °C.

• True

• False

(E) The number of neutrons in an atom is different from that in the ion formed by that atom.

• True

• False

What is molecule M?

• A. Gold

• B. Hydrogen

• C. Iron

• D. Sulphur

The table shows the atomic number and the mass number of element X.

How many protons and electrons does the atom of element X have?

• A. Number of protons: 19; Number of electrons:19

• B. Number of protons: 19; Number of electrons:20

• C. Number of protons: 20; Number of electrons:39

• D. Number of protons: 39; Number of electrons:19