Understanding Atoms

Everything around us is made of tiny particles called atoms. An atom is the smallest unit of an element that still keeps the properties of that element. Different elements are made of different kinds of atoms. For example, a hydrogen atom is different from an oxygen atom because they contain different numbers of particles inside them. 

Atoms are considered the building blocks of matter. Anything that has mass and occupies space is made of atoms, including water, air, food, plants, and even the human body. Although atoms are extremely small and cannot be seen by the naked eye, they play an important role in all physical and chemical changes.

An atom is made up of three main subatomic particles:

• Protons – positively charged particles found in the nucleus

• Neutrons – particles with no charge found in the nucleus

• Electrons – negatively charged particles moving around the nucleus

Atomic Mass and Atomic Weight

Since atoms are particles of matter, they also have mass. The atomic mass refers to the average mass of an atom of an element. It is measured in atomic mass units (amu). The atomic mass mainly comes from the protons and neutrons found in the nucleus because electrons have very little mass. Elements with more protons and neutrons usually have greater atomic masses.

The term atomic weight is often used together with atomic mass because they are closely related. Atomic weight refers to the average mass of all naturally occurring atoms of an element based on the abundance of its isotopes. In many chemistry lessons, atomic mass and atomic weight are used interchangeably because the values found on the periodic table represent the average masses of elements.

• Hydrogen (H) = 1 amu

• Carbon (C) = 12 amu

• Oxygen (O) = 16 amu

• Sodium (Na) = 23 amu

Atoms are the basic building blocks of matter, and each atom has its own mass called atomic mass. When atoms combine to form compounds, their atomic masses are added together to determine the formula mass of the substance. 

Conservation of Mass

When atoms combine to form compounds, their atomic masses are added together to determine the formula mass of a substance. During chemical reactions, the number of atoms is equal in both the reactant and the product.

The Law of Conservation of Mass states that mass cannot be created or destroyed during a chemical reaction. This means that the total mass of the reactants is always equal to the total mass of the products. In simpler terms, the atoms before the reaction are the same atoms after the reaction. They are only rearranged to form new substances.

For example, when hydrogen gas reacts with oxygen gas to form water, the atoms of hydrogen and oxygen do not disappear. They combine in a different arrangement to produce water molecules. Because no atoms are lost or gained, the total mass remains constant.