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All substances are made out of atoms.
In an atom, you'll find three sub-atomic particles. These are:
Protons and neutrons are found in the nucleus of an atom, which is right in the centre. Atoms can loose or get electrons, forming particles called ions. When an electron is lost, it becomes a positively charged ion. When an electron is gained, it becomes a negatively charged ion. |
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The number of protons in an atom's nucleus is called the atomic number.
All the atoms belonging to an element have the same amount of protons. The mass number is the total number of protons and neutrons. Look at the example to the right of oxygen as it is seen on the Periodic Table. The mass number is on the bottom- 15.999 but this is commonly rounded to 16. The number of protons is on the top which is 8. This means there are: 8 Protons. 8 Electrons A mass number of 16 To find the number of neutrons we minus the number of protons from the mass number Neutrons = mass number - proton number. Neutrons = 16 - 8 There are 8 neutrons in Oxygen REMEMBER SOME PERIODIC TABLES PUT THE MASS NUMBER ON THE TOP AND PROTON NUMBER ON THE BOTTOM |
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An isotope is an atom of an element with a different number of neutrons but a different number of protons and electrons.
This means isotopes have the same atomic number, but a different mass number.
An isotope can be radioactive or non-radioactive depending on its nucleus' stability.
This means isotopes have the same atomic number, but a different mass number.
An isotope can be radioactive or non-radioactive depending on its nucleus' stability.
Electrons are arranged in shells around the nucleus.
The first shell can only hold 2 electrons.
The second and third shells can hold 8. Shells after that can hold 18.
We write it from the first shell upwards e.g. Sodium = 2,8,1
The first shell can only hold 2 electrons.
The second and third shells can hold 8. Shells after that can hold 18.
We write it from the first shell upwards e.g. Sodium = 2,8,1