Atomic Number
Atomic Number
Atomic Number: It is defined as the number of protons present in the nucleus of an atom. All the atoms of the same element have the same of protons in their nuclei and hence, they have the same atomic number. It is denoted by Z and written as the subscript towards the left of the symbol. E.g. ,
, Z =2 and 3 for He and Li respectively.
Note: In neutral atom, atomic number = number of protons = number of electrons
Atomic Weight: Mass of an individual atom is called atomic mass or atomic weight. It is nearly equal to the mass number. It is nearly twice the atomic number for many atoms.
Carbon: atomic number (Z) = 6, Mass number (A) = 12, Atomic mass= 12.01 u
Oxygen: atomic number (Z) =8, Mass number (A) = 16, Atomic mass = 15.99 u
Note:
If atomic number of an element is 20, how many electrons are present in that element? | |||
| Right Option : D | |||
| View Explanation | |||
The number of electrons in a neutral atom of an element is equal to its: | |||
| Right Option : B | |||
| View Explanation | |||
An atom is electrically neutral because number of protons is ___________ | |||
| Right Option : C | |||
| View Explanation | |||
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