Here's a breakdown of why:

* Elements are the building blocks of matter: Everything around us is made up of elements. They are the simplest forms of matter that can exist.

* They cannot be broken down: Unlike compounds, which are made up of two or more elements combined chemically, elements cannot be separated into simpler substances through chemical reactions.

* They have unique properties: Each element has its own unique set of physical and chemical properties, such as melting point, boiling point, reactivity, and density.

Hydrogen and oxygen are distinct elements because they have their own unique properties and cannot be broken down into simpler substances.

Here are some key differences between hydrogen and oxygen:

Hydrogen:

* Atomic number: 1

* Symbol: H

* Gas at room temperature

* Highly flammable

* Colorless, odorless, and tasteless

Oxygen:

* Atomic number: 8

* Symbol: O

* Gas at room temperature

* Essential for respiration

* Colorless, odorless, and tasteless

In summary, hydrogen and oxygen are called elements because they are the simplest forms of matter with unique properties and cannot be broken down into simpler substances.