Introduction to Atom
7 Minutes
Atoms and molecules for kids explains what matter is, how atoms combine, and the types of molecules. A science lesson in English.
- What matter is and how Democritus and Kanada imagined the atom
- Silicon atoms, molecules, and common formulas like O2 and H2O
- Molecule types and how gaps between molecules form states of matter
What this lesson teaches
An atom is the smallest indivisible unit of matter, which is anything that occupies space and has mass. When two or more atoms join together, they form a molecule, which is how most substances exist.
Discovering atoms and molecules
Long ago, the Greek philosopher Democritus and the Indian philosopher Kanada imagined cutting an object like a cake repeatedly until reaching a size that could not be divided further. Atoms are so tiny that they cannot be seen with the naked eye or with an ordinary microscope. In the 1970s, scientists studied the surface of silicon and observed tiny, round ball-like shapes joined in groups of two or three, showing that atoms connect to form molecules.
Types of molecules by atom count
- Monoatomic molecules consist of only a single atom, and neon is an example.
- Diatomic molecules are made of two atoms joined together, such as an oxygen gas molecule.
- Triatomic molecules contain three joined atoms, such as water with two hydrogen atoms and one oxygen atom.
- Polyatomic molecules contain more than three atoms, such as chalk with one calcium, one carbon, and three oxygen atoms.
Molecules of elements and compounds
Molecules can also be grouped by the types of atoms they contain. In molecules of elements, only one kind of atom joins together, as seen in oxygen gas and chlorine gas. In molecules of compounds, different kinds of atoms combine, such as water, carbon dioxide, and the silicon dioxide found in soil. Oxygen is the most abundant atom on Earth because it is present in air, water, and soil, followed by silicon as the second most abundant atom.
How molecular spacing shapes matter
Matter exists in different states based on the size of the gaps between its molecules. When the gap between molecules is very small, the substance forms a solid. When the space between molecules is somewhat larger, the substance exists as a liquid. When the distance between molecules is very large, the substance behaves as a gas.