Element vs Compound: Oxygen vs Water in 3D
An element is made of only one kind of atom, such as oxygen or gold. A compound is two or more elements chemically joined in a fixed ratio, such as water, H2O. A compound can behave nothing like the elements it is made from.
Element vs compound at a glance
| Element | Compound | |
|---|---|---|
| Made of | One kind of atom | Two or more kinds of atom, chemically bonded |
| Ratio | Not relevant | Always fixed, like 2 hydrogen to 1 oxygen in water |
| Can be broken down by chemistry | No | Yes, into its elements |
| Shown by | A symbol, like O, Fe or Au | A formula, like H2O, CO2 or NaCl |
| How many | 118 known | Many millions |
| Examples | Oxygen, hydrogen, carbon, iron, gold | Water, carbon dioxide, table salt, sugar |
A compound is something new
Sodium is a soft metal that fizzes in water and chlorine is a poisonous green gas. Join them and you get sodium chloride, harmless table salt that you sprinkle on chips. Hydrogen burns and oxygen helps things burn, yet together they make water, which puts fires out. That is the clue that a chemical change has made a compound.
Compound or mixture?
In a mixture, substances are mixed but not bonded, and you can separate them by physical methods. Air is a mixture of nitrogen, oxygen and other gases. Salt water is a mixture of salt and water: boil off the water and the salt is left. To split a compound such as water into hydrogen and oxygen you need a chemical reaction, such as electrolysis.
Quick facts
- Some elements come as molecules: oxygen gas is O2 and nitrogen gas is N2.
- Every compound is made of at least two elements.
- Carbon forms more compounds than any other element.
- The 118 elements are arranged in the periodic table by their number of protons.
- Hydrogen is the most common element in the universe.
See them in 3D
Element vs compound questions
What is the difference between an element and a compound?
An element contains only one kind of atom. A compound contains two or more elements chemically bonded in a fixed ratio.
Is water an element or a compound?
A compound, made of hydrogen and oxygen in the ratio 2 to 1.
Is oxygen an element or a compound?
An element. Oxygen gas is made of O2 molecules, but both atoms are oxygen.
Is salt a compound?
Yes. Table salt is sodium chloride, a compound of sodium and chlorine.
Is air a compound?
No. Air is a mixture of gases that are not chemically bonded to each other.
More face-offs: see all 3D comparisons.
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