Molecule

A molecule is a group of atoms that are joined together by chemical bonds. These bonds hold the atoms tightly, forming the smallest unit of a substance that still has the same properties. Molecules can be very simple, like oxygen gas (O₂) made of two oxygen atoms, or very complex, like proteins that make up parts of living cells.

Atoms are like building blocks, and molecules are the structures built from them. For example, two hydrogen atoms and one oxygen atom form a molecule of water (H₂O). Every drop of water contains countless water molecules. In the air we breathe, there are molecules of nitrogen (N₂), oxygen (O₂), and carbon dioxide (CO₂). Each type of molecule has its own shape, size, and behavior, depending on how the atoms are connected.

Molecules can be made of the same type of atom or different types. When the same atoms join together, like in oxygen gas (O₂) or nitrogen gas (N₂), they are called elemental molecules. When different atoms join, such as in water or sugar, they form compound molecules. These combinations are what make up all the materials around us, from the food we eat to the air we breathe.

The way atoms bond in a molecule depends on their electrical attraction. Atoms can share electrons or transfer them to form stronger connections. These bonds decide how a molecule behaves. For example, water molecules stick to each other easily, which gives water its surface tension and allows small insects to walk on it.

Molecules also have movement. In gases, they move freely and quickly, spreading out in space. In liquids, they move more slowly but can slide past each other. In solids, molecules are packed closely and only vibrate in place. These motions explain why solids hold their shape, liquids flow, and gases fill the space they are in.

Studying molecules is an important part of chemistry. Scientists use special tools like microscopes and models to see how molecules are shaped and how they react with each other. Understanding molecules helps create new materials, medicines, and fuels that make modern life possible. In simple words, molecules are the tiny teams of atoms that make up everything in the world.