Atomic number-
We know that any atom contains three type of fundamental particles i.e. electron ,proton and neutron.
In any atom of protons indicates the Atomic number of that atom. According to Moseley (1913, working in Rurherford's lab) "the number of unit positive charges carried by the nucleus of an atom is termed as the Atomic number of that atom" .
Symbol of Atomic number is Z. The atomic number is also equal to the number of electrons.
It is an unique value, it means no two element can posses same atomic number.
Example: Atomic number of H is 1 and atomic number of carbon is 6.
"The sum of the number of proton and neutron in uncleus is termed as Mass number of an atom".It is denoted by A. We know that the mass of each proton and neotron are almost equal to 1 on the atomic mass scale, therefore the atomic mass of the atom is approximately equal to its mass number.
Example: Mass number of C is 12
Number of neutron in necleus N= A-Z
(wher A=Atomic mass and Z= Atomic number )
Atom with same atomic number but different neutrons number and hence different atomic masses called as Isotopes.
The term isotopes formed from the greek roots isos ( equal) and topos (place) , it means “the same place”. Thus , different isotopes of a single element occupy the same position on the periodic table.
The number of proton is called atomic number,it is equal to the number of electron,but the atom can have different numbers of neutron, thus each isotope of a given alement has a different mass number.
For example: carbon-12, carbon-13, carbon-14, where 12, 13, and 14 is the mass number of carbon atom respectively . Here ,in each isotope of carbon atom the number of electron is same i.e. 6, and the number of proton is also the same as electron i.e. 6, but number of neutron is different .
Carbon 12 = 6 neutrons
Carbon 13 = 7 neutron
- Carbon 14 = 8 neutrons.
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