Atoms, Molecules And Ions

Explanation
An oxygen molecule is composed of two oxygen atoms bonded together, so it has a total of two atoms.

Explanation
A molecule is formed when two or more atoms combine chemically. In other words, atoms are the building blocks of molecules. They join together through chemical bonds to form different types of molecules, such as water (H2O) or carbon dioxide (CO2). Therefore, the correct answer is atoms.

Explanation
Molecules of elements consist of a fixed number of the same type of atoms chemically combined. This means that in a molecule of an element, all the atoms present are of the same type. For example, a molecule of oxygen consists of two oxygen atoms chemically bonded together. Similarly, a molecule of hydrogen consists of two hydrogen atoms chemically bonded together. This is a defining characteristic of elements, as they are made up of only one type of atom.

Explanation
A compound is a substance made up of two or more different types of atoms that are chemically bonded together. The atoms in a compound are held together by chemical bonds, which can be either covalent or ionic. The fixed number of atoms in a compound is determined by its chemical formula, which shows the types and ratios of atoms present. Compounds have unique properties that are different from the properties of the individual elements that make them up.

Explanation
Glucose contains three different types of elements: carbon, hydrogen, and oxygen. These elements combine to form the molecular structure of glucose, which is C6H12O6. The carbon atoms provide the backbone of the molecule, while the hydrogen and oxygen atoms are attached to the carbon atoms, creating the functional groups and giving glucose its chemical properties.

Explanation
Carbon monoxide consists of 1 carbon and 1 oxygen atom. The chemical formula for carbon monoxide is CO, where C represents carbon and O represents oxygen. In this molecule, there is only one atom of each element present.

Explanation
A phosphorus molecule is made up of 4 phosphorus atoms. Each phosphorus atom contributes one electron to form a covalent bond with the other three phosphorus atoms, resulting in a stable molecule with a total of 4 phosphorus atoms.

Explanation
A sulphur molecule is made up of 8 sulphur atoms.

Explanation
Metals and noble gases such as helium and argon do not exist as molecules because they have stable electron configurations. Helium, specifically, is a noble gas with a full outer electron shell, making it highly stable and unreactive. Consequently, helium atoms do not need to bond with other atoms to achieve a stable configuration, and they exist as individual atoms rather than forming molecules.

Explanation
A water molecule consists of one oxygen atom and two hydrogen atoms.