Atoms, Elements, Molecules, Compounds, and Mixtures

What is the difference between an atom and an element? How are molecules different from atoms? I am often asked these questions in my sessions over and over again and so I finally decided to write a comprehensive post on them. Find answers to all your questions in this section that is designed to help students explore and understand the relationship between atoms, elements, molecules, compounds and mixtures in a manner that is simple and easy to understand. So, let’s begin!
  • What is an Atom?

    All the matter in the universe is made of tiny particles calledatoms. There are 92 different kinds of atoms in nature. These 92 different atoms combine with one another to form different kinds of matter that we see in nature.

    Gold, for example, is made of only gold atoms. When matter is made of only one kind of atom, it is called an element. In the same way, silver is another element which is made of only silver atoms. Because there are 92 different kinds of atoms in nature, there are 92 different kinds of elements. Other examples of an atom are K (potassium) and Fe (iron).

  • What are Elements?

    The element is the fundamental substance that consists of only one type of atom. Elements consist of smaller particles and can be man-made or synthetic. Their arrangement in the periodic table is based on the number of protons in an increasing order. The atomic number of an element is indicated by Z. When atoms are arranged differently in an element having the same number of protons, you get different forms of an element. For example, both graphite and diamond are elements of carbon but they look very different from each other.

  • What is a Molecule?

    A molecule is the smallest unit of a chemical compound and it exhibits the same chemical properties of that specific compound. As molecules are made up of atoms jointly held by chemical bonds, they can vary greatly in terms of complexity and size. The oxygen we breathe has a molecular formula O2. Should we consider this as an element or compound? When two or more atoms of the same elements combine together, we call them Molecules. So, we call O2 as an oxygen molecule. In the same way, we find hydrogen molecules H2, chlorine molecules Cl2 and others in nature.

  • What is a Compound?

    The chemical formula of water is H2O. Observe that, water is made of two hydrogen atoms and one oxygen atom. Here, two different elements, hydrogen and oxygen combine, giving rise to a new substance called water. Such substances, which are made by the combination of two or more kinds of elements are called Compounds. The atoms in a compound are chemically bonded and hence cannot be separated easily. Similarly, the chemical formula of carbon dioxide is CO2 and it is made up of two elements, carbon, and oxygen. Some other examples of compounds are table salt (NaCl), chalk (CaCO3)and water (H2O).

  • What is a Mixture?

    The mixture is a substance made by the physical combination of two or more different elements or compounds. A mixture does not involve any chemical reaction. So, if you mix the magnetized powder with sand, you get a mixture that can be separated physically by means of a magnet. It can be composed of solids, liquids or gases and can be classified into 6 different categories – homogenous, heterogeneous, solutions, alloys, suspensions, and colloids.

    An evenly distributed mixture of water and ethanoic acid is called vinegar and can be termed as a homogenous mixture. When two or more substances are not evenly distributed in a mixture, like a blend of oil and water, the mixture is called heterogeneous. When salt is dissolved in water, you get a solution and when you combine two heterogeneous fluids containing solid particles that settle at the bottom, you get suspensions. Colloids are formed when one substance in a heterogeneous mixture is evenly dispersed throughout the other substance, example milk. Alloys are mixtures of one or more metals in a solid solution. Bronze, steel, and brass are common examples of alloys.

    I hope this helps all our students to clear their doubts about the differences between atoms, elements, molecules, and mixtures.