Write the unit of mass and its definition.
Write the unit of mass and its definition.
The mass of an atom is very small compared to a kilogram, kilogram is not a very convenient unit to measure such small quantities.
In nuclear physics, the unit of atoms is taken as amu means atomic mass unit, it is also denoted by unified mass unit $(u).$
Definition : The twelfth part of the mass of unexcited carbon $\left(C^{12}\right)$ atom is called $1$ amu that is $1 \mathrm{u}$.
The mass of unexcited carbon atom is $1.992647 \times 10^{-26} \mathrm{~kg}$
$1\mathrm{u}=\frac{\text { Mass of unexcited carbon atom }}{12}$ $=\frac{1.992647 \times 10^{-26}}{12} \mathrm{~kg}$ $=0.166 \times 10^{-26} \mathrm{~kg}$ $1 \mathrm{u}=1.66 \times 10^{-27} \mathrm{~kg}$
The atomic masses of various elements expressed in atomic mass unit ' $u$ ' are close to being integral multiples of the mass of a hydrogen atom. However there are many striking exceptions to this rule.
Accurate measurement of atomic masses is carried out with a mass spectrometers.
Similar Questions
Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$
Assertion $A:$ The binding energy per nucleon is practically independent of the atomic number for nuclei of mass number in the range $30$ to $170$.
Reason $R$ : Nuclear force is short ranged.
In the light of the above statements, choose the correct answer from the options given below on
Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$
Assertion $A:$ The binding energy per nucleon is practically independent of the atomic number for nuclei of mass number in the range $30$ to $170$.
Reason $R$ : Nuclear force is short ranged.
In the light of the above statements, choose the correct answer from the options given below on
- [JEE MAIN 2023]
The nuclei ${ }_{6} C^{13}$ and ${ }_{7} N^{14}$ can be described as
The nuclei ${ }_{6} C^{13}$ and ${ }_{7} N^{14}$ can be described as
- [AIPMT 1990]
Which of the following figure represents the variation of In $\left(\frac{R}{R_{0}}\right)$ with $\ln A$ (If $R=$ radius of a nucleus and $A =$ its mass number)
Which of the following figure represents the variation of In $\left(\frac{R}{R_{0}}\right)$ with $\ln A$ (If $R=$ radius of a nucleus and $A =$ its mass number)
- [JEE MAIN 2022]
As compared $^{12}C$ atom, $^{14}C$ atom has
As compared $^{12}C$ atom, $^{14}C$ atom has
$(a)$ Two stable isotopes of lithium $_{3}^{6} L$ and $_{3}^{7} L$ have respective abundances of $7.5 \%$ and $92.5 \% .$ These isotopes have masses $6.01512\; u$ and $7.01600\; u ,$ respectively. Find the atomic mass of lithium.
$(b)$ Boron has two stable isotopes, $_{5}^{10} B$ and $^{11}_{5} B$. Their respective masses are $10.01294 \;u$ and $11.00931\; u$, and the atomic mass of boron is $10.811\; u$. Find the abundances of $_{5}^{10} B$ and $_{5}^{11} B$
$(a)$ Two stable isotopes of lithium $_{3}^{6} L$ and $_{3}^{7} L$ have respective abundances of $7.5 \%$ and $92.5 \% .$ These isotopes have masses $6.01512\; u$ and $7.01600\; u ,$ respectively. Find the atomic mass of lithium.
$(b)$ Boron has two stable isotopes, $_{5}^{10} B$ and $^{11}_{5} B$. Their respective masses are $10.01294 \;u$ and $11.00931\; u$, and the atomic mass of boron is $10.811\; u$. Find the abundances of $_{5}^{10} B$ and $_{5}^{11} B$