The Three Fundamental Particles:
Atoms are made up of three fundamental particles: Protons, Neutrons and Electrons.
Proton and neutrons are found in the nucleus and are collectively called nucleons. Electrons orbit the nucleus in a similar way to that in which planets orbit a Sunny. In between the electrons and the nucleus there is nothing (empty space).
The following table shows the basic properties of these three particles:
Proton and neutrons are found in the nucleus and are collectively called nucleons. Electrons orbit the nucleus in a similar way to that in which planets orbit a Sunny. In between the electrons and the nucleus there is nothing (empty space).
The following table shows the basic properties of these three particles:
Particle |
Charge |
Mass |
Proton |
+1 unit |
Approx 1 unit |
Neutron |
No charge |
Approx 1 unit |
Electron |
-1 unit |
Approx 1/1840 units (very small/virtually zero) |
What Do These Properties Tell Us?
Charge:
1 unit of charge is known to be 1.602 x 10^-19 Coulombs. A proton is given a charge of +1 and an electron is given a charge of -1. All charges are measured in these units.
Mass:
1 unit of mass is 1.661 x 10^-27 kg. This is also not a convenient number, so we use "atomic mass units". Since the mass of protons and neutrons varies slightly depending on the nucleus, then in order to define an "atomic mass unit" we need to choose one nucleus as a standard. For this purpose, C-12 was chosen because its mass per nucleon (1.661 x 10^-27 kg) is around average, which means all of the other nuclei have masses close to whole numbers. An atomic mass unit is thus defined as 1/12th of the mass of one atom of C-12. Everything else is measured relative to this quantity.
1 unit of charge is known to be 1.602 x 10^-19 Coulombs. A proton is given a charge of +1 and an electron is given a charge of -1. All charges are measured in these units.
Mass:
1 unit of mass is 1.661 x 10^-27 kg. This is also not a convenient number, so we use "atomic mass units". Since the mass of protons and neutrons varies slightly depending on the nucleus, then in order to define an "atomic mass unit" we need to choose one nucleus as a standard. For this purpose, C-12 was chosen because its mass per nucleon (1.661 x 10^-27 kg) is around average, which means all of the other nuclei have masses close to whole numbers. An atomic mass unit is thus defined as 1/12th of the mass of one atom of C-12. Everything else is measured relative to this quantity.