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The Atom

By Ria Aggarwal

Atoms make the world around us. They are known as the building blocks of all matter and chemistry. An atom is the smallest unit in which matter can be divided, as well as the smallest unit that has characteristics of a chemical property.

There are many different types of atoms: hydrogen atoms, oxygen atoms, carbon atoms, and many more. In fact, there are over 100 different types of atoms; around 92 of these happen naturally while the rest are made in a lab by scientists.

Atoms have the ability to combine with each other, forming molecules. An example of that is water. Two hydrogen atoms combine with one oxygen atom to form water, hence the formula H2O.

Knowing that molecules are made of atoms leads to the question, what are atoms made of?

Protons, Neutrons, and Elections

Atoms consist of three particles: protons, neutrons, and electrons. Protons have a positive charge, and neutrons have a neutral charge. They both lie in the center of the atom and form the nucleus, which is small and dense. Orbiting the nucleus are the electrons, which have a negative charge. The orbital path is called the shell, and each shell holds a certain amount of electrons. The first shell can hold a maximum of 2 electrons, the second and third can hold 8 electrons, the fourth and fifth can hold 18 electrons, and so on.

Basic Properties of an Atom

Atomic number

The atomic number is a critical characteristic when talking about an atom. The atomic number expresses the number of protons in the nucleus (or the number of electrons, since the number of protons and electrons are always equal) of the particular atom in discussion. The letter ‘Z’ is used to talk about atomic numbers. Different atomic numbers refer to different elements, which can be found on the periodic table. For example, an atom with a Z of 4 means that there are 4 protons in the nucleus, also referred to as beryllium. On the other hand, an atom with a Z of 8 refers to the element oxygen.

Atomic mass and isotopes

The mass of an atom is affected by the number of neutrons in the nucleus. This does not affect the chemical properties as this is influenced by the number of protons in the nucleus of the atom.

Atoms that have nuclei containing the same number of protons but different numbers of neutrons are considered to be isotopes of each other. Isotopes are characterized by giving the sum of the protons and neutrons in the nucleus, which is known as the atomic mass number.


Atoms are very unique particles. However, what is covered in this article about atoms is just a few of the basics. There is so much more to know when it comes to the atom, and it starts with them building the entire foundation of chemistry.


Photo references:

  1. Biomedical Sciences Ph. D., Physics and Mathematics B. A., Facebook Facebook, Twitter Twitter, 2020,

  2. Anon, teachoo,


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