Please read the post on my blog name “ The Atom” to make the topic more easy to understand. Click here to read.
What are isotopes and how are they different from each other?
Dalton’s atomic theory suggested that all atom of an element are identical, but this was proven to be incorrect. It was shown that some atom have more mass than other atom of the same element.
It’s known that atoms are electronically neutral, because the number of protons equal the number of electrons (if 10 protons are present in an atom, then 10 electrons will also be present in the atom). Every atom of a particular element contains the same number of protons. The number of protons present in an atom is called the proton number or atomic number of the element and is represented by the symbol Z.
It is important to note that the mass derived from the protons and electrons is the same for every atom of the element. But the number of neutrons in atoms of the same element are not always the same. The differences in the number of neutrons in atoms of the same element basically accounts for the difference in the mass of isotopes.
Therefore isotopes are atoms of the same element that have different mass number, because the number of neutrons in the atoms of the element is different.
Two elements that have isotopes are carbon and chlorine. To identify an isotope the element symbol and mass number are basically all you need to do so. Therefore the atomic number is sometime excluded.