what is Atomic number and atomic mass

Atomic number is simply the number of protons present inside the nucleus of an atom whereas the atomic mass is the number of protons and neutrons present in the atomic nucleus so when we have to represent both these entities for an element how do we write it is there a specific way for representing it yes the chemical symbol of the element is written with atomic number at its bottom on the left side that is in subscript on the other hand the atomic mass is written on the top left side in superscript something like this the symbol of the element its atomic number, and its atomic mass now how do we represent a simple elements like carbon that's right something like this the atomic symbol that is C followed by the atomic number six an atomic mass 12 at the respective places now what if it's another element say chlorine something one type of chlorine atom can be represented like this why did I say one type of chlorine atoms are there more types of chlorine atoms yes some chlorine atoms have 20 neutrons instead of 18 in the nucleus then how do we represent this type yes just like this representation however we now need to understand what exactly that is there are many such cases where atoms of the same element exist in different forms these forms are called the isotopes yes in simple words isotopes are defined as the atoms of the same element having the same number of protons but different number of neutrons yes same number of protons but different number of neutrons just as we saw in the case of chlorine all the atoms have 17 protons but a few of them have 18 neutrons while some others have 20, so these are the topic forms of chlorine similarly several elements have isotopic forms for instance we have carbon with three isotopes as we can see here each isotope has six protons but different number of neutrons one has six the other has seven and the last one with eight neutrons we name these isotopes as carbon-12 carbon-13 and carbon-14 respectively now this was about the different forms of the same element but what if I tell 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 element′s Sulfur potassium calcium chlorine and argon now if you notice in each case the number of protons and neutrons is different it's 16 and 24 here 19 and 21 here and so on that's right however the total number of nucleons in each sums up to 40 what do we mean by a nucleon is a proton or a neutron yes each state present in a nucleus is a nucleon so 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 but the sum of protons and neutrons is the same as the atomic mass of the atom so coming back to our example there are five different atoms here though the number of protons and the number of neutrons is different in each case the total number of nucleons in each is the same which means the atomic masses are the same how 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's 16 plus 24 next is the potassium isotope having 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 are called as isobars the term arises from Greek ISO meaning same and barrows meaning weight remember if we considered two isobars the number of protons and number of neutrons in each case will be different but the total number of nucleons or the atomic masses will be the same so far we've understood subatomic particles and a few important concepts related to atoms