The atom is the smallest particle of a chemical element that can exist while retaining the same properties as the original element.
Atoms are made up of three main components, neutrons, protons and electrons.
- Protons are positively charged and are found in the nucleus.
- Neutrons are the particles that keep the atom together. without neutrons, the protons would repel each other, and these would act as a barrier to the protons. These do not have a charge.
- Electrons are negatively charged particles which are orbiting around the nucleus.
The mass of the protons and neutrons is more or less equivalent while the mass of the electron is much lower, and thus only the mass of the protons and neutrons is considered relevant for the mass of the atom.
The periodic table contains a lot of information. The numbers of the neutrons, electrons and protons can all be found using such information.
Proton Number = Atomic number
Neutron Number = Mass number – Atomic Number
Electron Number = Atomic Number – Charge
Once the number of electrons has been established these should be drawn into shells.
Each shell can take up a number of different electrons, but for the intents of this chapter the first shell takes in 2 electrons, the second shell takes in 8 electrons, the third shell takes in 8 electrons and the in the fourth shell the maximum number of electrons that will be put in it is going to be 2 electrons.
For example:
Oxygen has 8 electrons, therefore these will be placed in shells as 2 in the first shell, and 6 in the second shell, being written as 2, 6.
Calcium has 20 electrons, therefore these will be placed in shells as 2 in the first shell, 8 in the second shell, 8 in the third shell and the final 2 in the fourth shell, being written as 2, 8, 8, 2.
In order to draw these atoms with electrons around them, one should draw the nucleus, either as the letter of the element or the number of protons and neutrons, and shells around it. The electrons are then depicted as either dots or crosses.
Isotopes
The nucleus can be considered to be the heart of the atom, where the protons indicate the composition of the atom while the neutrons indicate the radioactivity of the nucleus.
This statement shows that a change in the proton number would change a nucleus from one element to another while a change in the neutron number will only change the stability of the nucleus. An isotope is when an element would have a nucleus with the same number of protons but a different number of neutrons. This explains the fact that no element has got a whole mass number due to the fact that this would be the average of all of the elemental nuclei.