What is formed when atoms join together?

When atoms join together, they form a molecule. A molecule is a group of two or more atoms bonded together through chemical bonds. This bonding can occur in various ways, including covalent bonding, where atoms share electrons, or ionic bonding, where electrons are transferred between atoms. Molecules can consist of the same type of atom, like O2, which is a molecule of oxygen, or different types of atoms, such as H2O, which is a water molecule composed of hydrogen and oxygen.

Understanding molecules is fundamental in chemistry, as they represent the smallest units of substances that retain the properties of those substances. Compounds, for instance, are specific types of molecules that contain at least two different types of elements chemically bonded together, which distinguishes them from simple molecules made up of identical atoms. Mixtures consist of two or more substances that are combined physically rather than chemically, meaning their individual chemical properties remain unchanged. Ions, on the other hand, are charged atoms or molecules that have either gained or lost electrons, and while ions can form compounds and molecules, they themselves are distinct entities. Therefore, the correct answer emphasizes the formation of molecules as a fundamental concept in understanding chemical interactions.