Mass Number
Mass Number
Mass Number: It is defined as the sum of number of protons and neutrons in the nucleus of an atom. Protons and neutrons together are called as nucleons. Mass number is denoted by A. Mass number (A) = Number of protons + number of neutrons. Eg: He, Li, At. mass = 4 and 7 for He and Li respectively.
Number of neutrons = Mass number - atomic number
Atomic number = Number of protonsMass number is written as a superscript towards the left of the symbol. In the notation for an atom, the atomic number, mass and symbol of the element are to be written as:
Here, the mass number of helium, lithium, sodium are 1, 7, 23 respectively.
If a dispositive ion of an element X consists of 12 protons and 12 neutrons and another dispositive ion of an element Y consists of 18 electrons and twice the number of electrons of dispositive ion X is the number of neutrons of Y, then, the mass number would be in the ratio of | |||
| Right Option : B | |||
| View Explanation | |||
Identify the number of neutrons present in pair of elements with atomic numbers 20 and 13, if their mass numbers are 40 and 27, respectively. | |||
| Right Option : D | |||
| View Explanation | |||
The number of neutrons is equal to the number of protons present in the nucleus of two elements and their respective dinegative ions posses 8 electrons in the L and M shells, respectively. Then the ratio of mass numbers of the two elements is ____________ | |||
| Right Option : A | |||
| View Explanation | |||
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