Chemical Element

atoms · periodic table · chemistry · building blocks

Protons define it. Every element is different because of the number of protons in its nucleus. Oxygen has 8 protons, gold has 79, and hydrogen has just 1. That number is called the atomic number, and it's what makes each element unique.

Isotopes are cousins. Atoms of the same element can have different numbers of neutrons, creating versions called isotopes. For example, carbon usually has 6 neutrons, but carbon-14 has 8. They're the same element but slightly different.

Elements can transform. In nuclear reactions, atoms can actually change into completely different elements by gaining or losing protons. This is how scientists create new elements in labs and how the sun powers itself.

Everything is made of them. Almost everything in the entire universe, from stars to planets to you, is made from chemical elements. There are over 100 known elements, and they combine together to create every object you can see.