Mass of one atom of an elements called atomic mass. OR
The total number of protons and neutron in an atom. OR
Atomic mass Of an elements may be defined as the average relative mass of an atom of the elements as compared With mass Of an atom of carbon. OR
The atomic mass is expressed to how many times an atom of substance is heavier Than 1/12th . Mass of carbon -12 atom.
- Atomic mass unit ( earlier abbreviated as amu but according to the latest IUPAC recommendations it is now written as ‘u’ that is unified mass.
- Atomic mass unit (amu) or unified mass (u).
- For example When we buy anything like fruits, vegetables, cereals, etc. We take in kilogramme, we took reference of weight to compare or measure the things , like we calculate the 1kg of vegetables we took another side weight 1kg exactly like other pan we take vegetables,
So we conclude that we took mass we have to need reference something .
In atomic mass we took as a reference 12C that is carbon twelfth is 12 amu or 12u.
- 12 amu is weight = one carbon atom.
- 1 amu or u = 1/ 12 Weight of one 12C atom.
- One atomic mass unit is mass unit equal to exactly one twelfth (1/12th) the mass of one atom of carbon-12 .
- For Example
- In 1961 for a universally accepted atomic mass unit carbon-12 isotope chooses as a standard reference for measuring atomic mass.
- Carbon-12 is presents in abundantly ( large numbers) in everywhere.
- Carbon-12 are moderately reactive.
- How the value of carbon-12 1/12 are 1.6605×10-24
1 amu or 1 u = 1/12 ×mass of 12C atom
= 1/12× 1.9926 ×10-24
1 amu or 1 u = 1.6605×10-24
- For example atomic mass of hydrogen ,
Formula:
Sr. No |
Elements | Mass | Mass in ‘u’ |
1 | Hydrogen | 1.6736×10-24kg |
1.0007u or 1 |
2 |
Helium | 1.6605×10-24 kg | 4.0026u or 4 |
3 | Carbon | 1.9926×10-24 kg |
12 u 12 |
4 |
Nitrogen | 2.3253×10-26 kg | 14.0031u or 14 |
5 | Oxygen | 2.6560×10-26 kg |
15.9949 u or 16 |
6 |
Fluorine | 3.1548×10-26 kg | 18.9948u or 19 |
7 | Aluminium | 4.4804×10-26 kg |
26.9815 u or 27 |
8 |
Cobalt | 9.7861×10-26 kg |
58.9332 u or 59 |
Question Answer:
1) What is atomic mass?
Answer: Mass of one atom of an elements called atomic mass. OR
The total number of protons and neutron in an atom.
2) What is unit of atomic mass?
Answer : Unit of atomic mass is amu (atomic mass unit) or ‘u’ ( unified mass) .
3) Why carbon-12 used as a reference atom?
Answer: In 1961 for a universally accepted atomic mass unit carbon-12 isotope chooses as a standard reference for measuring atomic mass. Carbon-12 is presents in abundantly ( large numbers) in everywhere.Carbon-12 are moderately reactive. That is why carbon-12 used as a reference atom.
4) Calculate the Hydrogen atomic mass?
Answer: Formula: