LEARNING OBJECTIVES:
- What is an Atom?
- What is the Building Block of Chemistry?
- What is the Structure of the Atom?
- What are Atomic Particles?
- What is the Mass and Charge of Basic Subatomic Particles?
- What is the Net Charge on an Atom?
ATOM - THE BUILDING BLOCK OF CHEMISTRY
The atom is the smallest and most fundamental unit of matter. Matter is anything that occupies space and has mass. Atoms are composed of subatomic particles such as protons, neutrons, and electrons. These particles define the properties of atoms and influence the behavior of matter in chemical reactions.
In a chemical reaction, atoms rearrange themselves to form molecules. The atoms, their numbers, and their arrangement determine the chemical properties of the resulting molecule. For instance, water (H2O) is composed of 2 hydrogen atoms and 1 oxygen atom. However, when 2 hydrogen atoms and 2 oxygen atoms combine, they form hydrogen peroxide (H2O2).
Learn more about this in Chemistry and its disciplines.
Atomic Particles
The atom consists of a nucleus, which contains protons and neutrons, and electrons that orbit the nucleus in shells. Protons are positively charged, neutrons are neutral, and electrons are negatively charged. The electrons orbit around the nucleus in defined paths called electronic shells.
Mass and Charge of Particles
The mass of a proton is nearly equal to the mass of a neutron. However, the electron is much lighter—about 1836 times lighter than a proton and 1840 times lighter than a neutron.
- Mass of proton = 1.673 X 10-27 kilograms
- Mass of neutron = 1.675 X 10-27 kilograms
- Mass of electron = 9.109 X 10-31 kilograms
The charge on the electron and proton is the same in magnitude (1.6 X 10-19 C) but opposite in sign. Protons have a positive charge, electrons have a negative charge, and neutrons carry no charge.
The Net Charge on the Atom
An atom is electrically neutral, meaning the number of protons in the nucleus is equal to the number of electrons orbiting the nucleus. Since protons carry a charge of +1 and electrons carry a charge of -1, their effects cancel each other out, resulting in a neutral atom.
For example, a helium atom contains 2 protons, 2 neutrons, and 2 electrons. The net charge on a helium atom is:
(+1 X 2) + (0 X 2) + (-1 X 2) = 0
SUMMARY:
- Atom is the basic building block of chemistry.
- Atoms are composed of subatomic particles such as electrons, protons, and neutrons.
- Protons and neutrons are heavier than electrons, but protons have a positive charge, electrons have a negative charge, and neutrons are electrically neutral.
- Atoms combine to form different molecules, each with unique properties.
- Atoms are electrically neutral, with an equal number of protons and electrons.