Why is Helium a Pure Substance? (+ 3 Facts to Know)

Yes, helium is a pure substance. Helium is considered a pure substance because it consists of only one type of atom, which is helium itself. It is not composed of different elements or compounds, and its chemical and physical properties remain constant throughout. ¹

Well, this was just a simple answer. But there are few more things to know about this topic which will make your concept super clear.

So let’s dive right into it.

Explanation: Why is helium a pure substance?

Helium is considered a pure substance because it consists of only one type of atom, specifically helium atoms. In chemistry, a pure substance is defined as a material that has a fixed composition and distinct properties. It is composed of only one type of particle, either atoms, molecules, or ions. ²

Helium (He) is a chemical element with atomic number 2 on the periodic table. ³ It is the second lightest element and belongs to the noble gas group. Helium atoms consist of two protons, two neutrons, and two electrons. ⁴

Since it consists of only helium atoms and does not contain any other elements or compounds, it is classified as a pure substance.

Pure substances can exist in different states, such as solid, liquid, or gas. Helium, in its natural state, is a gas and is commonly known for its low boiling and freezing points, which are the lowest among all the elements. ^{5 6}

It remains in a gaseous state at normal temperatures and pressures, making it widely used in various applications, including cooling superconducting magnets, filling balloons, and as a component in certain industrial processes. ⁷

In summary, helium is considered a pure substance because it is made up of a single type of atom, helium atoms, and does not contain any impurities or other substances.

Why is helium not a mixture?

Helium is not a mixture because a mixture consists of two or more different substances that are combined physically but retain their individual properties. In the case of helium, it consists of only one type of atom, helium atoms, and does not contain any other substances.

Mixtures can be classified into two types:

1. Homogeneous and 
2. Heterogeneous

Homogeneous mixtures have a uniform composition throughout, whereas heterogeneous mixtures have non-uniform compositions and contain visibly distinct components. ⁸

In the case of helium, it is composed solely of helium atoms, and there is no variation in its composition or properties within the sample. It is a pure element and not a combination of different substances. Therefore, helium does not fit the definition of a mixture, which requires the presence of multiple distinct substances.

In contrast, if we were to consider a scenario where helium gas is mixed with another gas, such as oxygen or nitrogen, then it would be considered a mixture because it would contain two or more different substances combined physically. However, in its pure form, helium is not a mixture but a pure substance.

Helium is a pure substance, but is it an element or a compound?

Helium is an element. Helium, with the atomic number 2, is the second lightest element on the periodic table. It consists of helium atoms, each containing two protons, two neutrons, and two electrons. ⁹ As an element, helium retains its individual properties and cannot be further decomposed into simpler substances.

On the other hand, compounds are substances composed of two or more different elements chemically bonded together in fixed ratios. ¹⁰ They can be broken down into their constituent elements through chemical reactions. However, helium is not a compound since it consists of only one type of element, helium itself.

In summary, helium is an element, not a compound. It is a pure substance composed of only one type of atom, helium atoms, and cannot be broken down into simpler substances by chemical means.

Further reading

Why is Gold a Pure Substance?
Is Air a Pure Substance?
Why is Table Salt a Pure Substance?
Why is Silicon a Metalloid?
Is Sulfur a Metal? 

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