The Atom

The concept of the atom has been around since ancient times, but it wasn’t until the late 19th century that scientists began to understand the true nature of atoms. Today, we know that atoms are the basic building blocks of matter and that everything in the world is made up of atoms. In this lesson, we will explore the structure of the atom and its significance in the world of chemistry.

The Structure of the Atom

The atom is made up of three basic particles: protons, neutrons, and electrons. Protons and neutrons are found in the nucleus, or center, of the atom, while electrons orbit around the nucleus in shells or energy levels.

Protons have a positive charge, neutrons have no charge, and electrons have a negative charge. The number of protons in an atom’s nucleus determines the element it is, while the number of neutrons and electrons can vary.

The Atomic Number and Mass Number

The atomic number of an element is the number of protons in the nucleus of its atom. For example, all hydrogen atoms have one proton in their nucleus, so the atomic number of hydrogen is 1.

The mass number of an atom is the sum of its protons and neutrons. For example, a hydrogen atom with one proton and no neutrons has a mass number of 1.

 Isotopes and Ions

Isotopes are atoms of the same element that have different numbers of neutrons. For example, carbon-12 has six protons and six neutrons, while carbon-14 has six protons and eight neutrons. Isotopes have the same atomic number but different mass numbers.

Ions are atoms or groups of atoms that have a net electric charge. This can happen when an atom gains or loses electrons. If an atom gains electrons, it becomes negatively charged and is called an anion. If it loses electrons, it becomes positively charged and is called a cation.

Atoms are the basic building blocks of matter, and understanding their structure is essential to understanding chemistry. By knowing the basic parts of an atom, its atomic number and mass number, and the differences between isotopes and ions, we can better understand the properties and behaviors of different elements and compounds.

Periodic Table of Elements