Molecule Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Molecule.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

The smallest unit of a covalent substance, consisting of two or more atoms held together by chemical bonds (typically covalent), acting as a single distinct particle with specific chemical properties.

Atoms stuck together. Water (\text{H}_2\text{O}) is one molecule with 3 atoms.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Molecules have specific fixed ratios of atoms held together by covalent bonds.

Common stuck point: Molecules can be elements (\text{O}_2) or compounds (\text{H}_2\text{O}).

Sense of Study hint: When identifying whether something is a molecule, check if it is a discrete unit of covalently bonded atoms. First determine if the substance is covalent (shares electrons) or ionic (transfers electrons). Then count the atoms — a molecule must have at least two. Finally, note that ionic compounds like \text{NaCl} form lattices, not individual molecules.

Worked Examples

Example 1

easy
Define a molecule and explain the difference between a molecule of an element and a molecule of a compound.

Solution

  1. 1
    A molecule is a group of two or more atoms held together by covalent bonds, acting as a single unit.
  2. 2
    A molecule of an element contains only one type of atom: e.g., \text{O}_2 (two oxygen atoms), \text{N}_2 (two nitrogen atoms).
  3. 3
    A molecule of a compound contains two or more different types of atoms: e.g., \text{H}_2\text{O} (hydrogen and oxygen), \text{CO}_2 (carbon and oxygen).

Answer

\text{Molecule of element: O}_2\text{. Molecule of compound: H}_2\text{O.}
The term molecule specifically refers to covalently bonded groups of atoms. Ionic compounds like NaCl form crystal lattices rather than discrete molecules, so they are described by formula units instead.

Example 2

medium
The molecular formula of glucose is \text{C}_6\text{H}_{12}\text{O}_6. How many total atoms are in one molecule of glucose? How many molecules are in one mole of glucose?

Example 3

medium
How many atoms are in one molecule of \text{C}_6\text{H}_{12}\text{O}_6 (glucose)? How many molecules are in 1 mole of glucose?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
Explain why \text{O}_2 and \text{O}_3 (ozone) are both molecules of the same element but have different properties.

Example 2

hard
A molecule of aspirin has the formula \text{C}_9\text{H}_8\text{O}_4. Calculate the total number of atoms in one molecule, the molar mass, and the number of hydrogen atoms in 0.50 mol of aspirin.
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Background Knowledge

These ideas may be useful before you work through the harder examples.

atomchemical bond