An element is a pure chemical substance consisting entirely of atoms that all have the same number of protons in their atomic nuclei. This number of protons is called the atomic number and uniquely identifies each element. Because all atoms of an element share the same atomic number, they exhibit the same chemical properties
. Elements cannot be broken down into simpler substances by ordinary chemical means, making them the fundamental building blocks of matter. They are made up of only one type of atom, distinguishing them from compounds and mixtures
. There are currently 118 known elements, with about 94 occurring naturally on Earth and the rest synthesized artificially. Elements are organized in the periodic table, which groups them based on similar chemical properties
. Examples of elements include hydrogen (atomic number 1), carbon (6), oxygen (8), gold (79), and mercury (80). Atoms of an element may have different numbers of neutrons, forming isotopes, but these isotopes share the same chemical characteristics because they have the same number of protons
. In summary, an element is:
- A pure substance made of only one kind of atom
- Defined by the number of protons in its atoms (atomic number)
- Unable to be broken down into simpler substances by chemical means
- A fundamental constituent of all matter in the universe
