Isotopes
atomThe smallest part of an element that can exist. of an elementA substance made of one type of atom only. that have the same number of protonSubatomic particle with a positive charge and a relative mass of 1. The relative charge of a proton is +1., but different numbers of neutronUncharged subatomic particle, with a mass of 1 relative to a proton. The relative charge of a neutron is 0. in their nucleiNuclei is the plural of nucleus. The nucleus is the central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. are called isotopeAtoms of an element with the same number of protons and electrons but different numbers of neutrons.. Isotopes of an element can be easily identified because:
- their atomic numberThe number of protons in the nucleus of an atom. Also called the proton number. is the same
- but their mass numberThe number of protons and neutrons found in the nucleus of an atom. are different
Three isotopes of hydrogen
All hydrogen atoms contain one proton and one electronSubatomic particle, with a negative charge and a negligible mass relative to protons and neutrons., but they can contain different numbers of neutrons. Hydrogen-1 is the most abundanceIf there is a lot of something, it is described as being abundant. isotope of hydrogen.
| Name of isotope | Symbol | Protons | Neutrons | Electrons |
| Hydrogen-1 | \(_{1}^{1}\textrm{H}\) | 1 | 1 - 1 = 0 | 1 |
| Hydrogen-2 | \(_{1}^{2}\textrm{H}\) | 1 | 2 - 1 = 1 | 1 |
| Hydrogen-3 | \(_{1}^{3}\textrm{H}\) | 1 | 3 - 1 = 2 | 1 |
| Name of isotope | Hydrogen-1 |
|---|---|
| Symbol | \(_{1}^{1}\textrm{H}\) |
| Protons | 1 |
| Neutrons | 1 - 1 = 0 |
| Electrons | 1 |
| Name of isotope | Hydrogen-2 |
|---|---|
| Symbol | \(_{1}^{2}\textrm{H}\) |
| Protons | 1 |
| Neutrons | 2 - 1 = 1 |
| Electrons | 1 |
| Name of isotope | Hydrogen-3 |
|---|---|
| Symbol | \(_{1}^{3}\textrm{H}\) |
| Protons | 1 |
| Neutrons | 3 - 1 = 2 |
| Electrons | 1 |
An isotope is named after the element and the mass number of its atoms. For example, carbon-12 is an isotope of carbon with a mass number of 12.
All three isotopes of hydrogen have identical chemical propertiesA description of how a substance reacts with other substances. For example, flammability, pH, reaction with acid, etc.. This is because the number of electrons determines chemical properties, and all three isotopes have one electron in their atoms.
Learn more on isotopes in this podcast.
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Question
The atomic number of carbon is 6. How many neutrons are there in the nucleus of a carbon-12 atom?
Number of neutrons = mass number - atomic number
= 12 - 6
= 6
Question
How many neutrons are there in the nucleus of a carbon-13 atom?
Number of neutrons = mass number - atomic number
= 13 - 6
= 7