Elements and the Periodic Table

An element is a pure substance that cannot be broken down into simpler substances by chemical means. It consists of only one type of atom.

A compound is a substance formed when two or more different elements are chemically bonded together. For example, water (H2O) is a compound made of hydrogen and oxygen.

A mixture is a combination of two or more substances that are not chemically bonded. Each substance retains its own properties. For example, a salad is a mixture.

The periodic table is a tabular arrangement of all known chemical elements, organized by increasing atomic number and grouped by similar properties.

The atomic number is the number of protons in the nucleus of an atom, which determines the element's identity.

The symbol for Oxygen is O.

Noble gases are a group of elements in Group 18 of the periodic table that are characterized by their lack of reactivity due to having a full valence shell of electrons.

The symbol for Iron is Fe.

There are 4 atoms of Oxygen in the compound CuSO4.

A molecule is the smallest unit of a chemical compound that retains its chemical properties, consisting of two or more atoms bonded together.