Isotopes and Isobars | Atoms and Molecules | Don't Memorise

By now we know exactly what the concept of atomic number and atomic mass is. Atomic number is simply the number of protons present within the nucleus of an atom, while atomic mass is the number of protons and neutrons present in the atomic nucleus, so when we have to represent both entities for an element, how do we write it? Is there a specific way to represent it? Yes, the chemical symbol of the element is written with the atomic number at the bottom of the left side, which is otherwise subscripted. The atomic mass is written at the top left in superscript, something like this, the element's symbol, its atomic number, and its atomic mass.

Now how do we represent simple elements like carbon? That's right, something like this, the atomic symbol which is C followed by the atomic number six an atomic mass 12 in the respective places now, what if it's another element? say chlorine something like this maybe yes, a type of chlorine atom can be represented like this why did I say a type of chlorine

atoms

? Are there more types of chlorine?

atoms

yes, some chlorine atoms have 20 neutrons instead of 18 in the nucleus, so how do we represent this type? Yes, like this representation, however, now we need to understand what exactly it is.

There are many cases where atoms of the same element exist in different ones. forms these forms are called

isotopes

yes, in simple words,

isotopes

are defined as atoms of the same element that have the same number of protons but different number of neutrons yes, the same number of protons but different number of neutrons as we saw in the case of Chlorine: all atoms have 17 protons, but some of them have 18 neutrons, while others have 20, so these are the thematic forms of chlorine. Similarly, several elements have isotopic forms, for example, we have carbon with three isotopes, as we can see each isotope here.

It has six protons but a different number of neutrons, one has six, the other has seven and the last one with eight neutrons we call these isotopes carbon-12, carbon-13 and carbon-14 respectively. Now it's about different forms of the same element, but what if I told you that atoms of two different elements can have the same atomic mass? Yes, let's understand this with an example, we take five different elements: sulfur, potassium, calcium, chlorine and argon, now if you notice that in each case the number of protons and neutrons is different. They are 16 and 24 here, 19 and 21 here and so on, that's right, however, the total number of nucleons in each adds up to 40, what do we mean by nucleon?

A nucleon is a proton or a neutron. Yes, each state present in a nucleus is a. nucleon then the total number of nucleons in an atom is the sum of protons and neutrons we can also say that the total number of nucleons in an atom is its atomic mass yes, understand this well the total number of nucleons which is nothing more than the sum Protons and neutrons are the same as the atomic mass of the atom, so returning to our example, here there are five different atoms, although the number of protons and the number of neutrons is different in each case, the total number of nucleons in each one it is the same. which means that the atomic masses are the same.

Yes, it's simple math. One of the sulfur isotopes that we have taken as an example has 16 protons and 24 neutrons, so the atomic mass of this isotope has to be 40 units, that is, 16 plus 24. The next is the potassium isotope that has 19 protons and 21 Newt, so again we get the atomic mass as four units and similarly we get the atomic mass as four units in each of the remaining cases such atoms or rather isotopes of different elements having the same atomic mass They are called

isobars

. The term arises from the Greek ISO, which means equal, and tumuli, which means weight.

Remember that if we consider two

isobars

, the number of protons and the number of neutrons in each case will be different, but the total number of nucleons or the atomic masses will be the same. same until now You already understood subatomic particles and some important concepts related to atoms. Now let's go ahead and learn the important concept of valence in the next lesson.