They are elements.
A substance made up of only one kind of atom is an element, which is a pure substance.
An element.
an element
A substance made up of only one kind of atom is an element.
element
hydrogen
yes
Element
An element is a substance made of only one kind of atom. Each element has a unique atomic number, which represents the number of protons in its nucleus. Examples of elements include oxygen, gold, and carbon.
Element
compound
yes