Relative Atomic Mass

Atom is an extremely small particle. It is not possible to weigh it directly. Therefore we take its mass by comparing with slected Standard Atomic mass of C-12 (the  stable light isotope of carbon)
Atomic mass is defined as the mass of one atom of the element compared with the mass of one atom of C-12.

It is a number which tells how heavy or light an atom is as compared to the mass of another atom.
The atomic mass of "Mg" is 24 which mean each atom of Mg is twice as heavy as Carbon atom.

A Swedish chemist J. Berzelius (1779-1848) determined the atomic masses of elements.
Atomic is the average of the masses of all the isotopes of an element with respect to their relative abundance.
It is determined by multiplying the masses of all the isotopes which relative abundance and then add them up and finaly divide them by 100.
For example:- Average Atomic Mass of Cu =63.55 a.m.u

Mass spectrometer is a technique by means of which the relative abundance and atomic mass of the element can be determined by Mass Spectrometer.

 Unit of Atomic Mass:-
Average mass of an atom is not absolute mass it is a relative mass hence has no unit. It is unit less quantity.

Atomic Mass Unit (a.m.u):-Generally atomic masses are expressed in atomic mass units (a.m.u). This is unit that describes the mass of a single atom. One single atom of Carbon has a mass of 12 a.m.u. This is very small. It may be defined as 1/12th part of the mass of one atom of C-12.

Comments

Post a Comment

Popular posts from this blog

My Favourite Game Cricket Essay

Image
Cricket was the national game of England. It has now become the second national game of Pakistan too, The top six cricket teams of the world at present are Australia, India, Srilanka, New Zealand, England South Africa, Pakistan and West Indeas. The first cricket club in England was hambled which existed till 1825. This game is placed upon a large piere of levelled ground. Generally, It is played on turf. Batting is done on the pitch. On this pitch stumps are fixed 22 yards aparts. There are 3 stumps on each side. On the top of these stumps are placed two balls. There are two umpires, one at each set of stumps. There cricket match is played between two teams of eleven players each. Before the play, captains of both teams go to the umpires for toss. The winner of the toss has choice to bat or field first, Six players generally stand on the right or off side of the batsman at long off, cover point, short slip long slip and square mid-on and long-on, The man behind the wicket is cal
Read more

Blessing Of Science Essay

Image
Science has made great progress today. Now inventions have changed our lives completely. Man is leading a comfortable and luxurious life as a result of blessings of science. The greatest achievement of science is the fastest means of communication. People are in touch with each other around the globe with the help of phones, e-mails, faxes and satellite phones. The distances have reduced and people reach from one corner of the world to the other in supersonic jets. Harmful diseases have been eradicated with the advancement in health science. The life expectancy is increasing day by day. Food production has increased with the research in agricultural science. The ever increasing population of the world can go on eating without the fear of hunger or famine. New entertainments are available to people who can watch a large number of TV channels on cable. Mass production in modern industries is responsible for meeting needs of people. Science is providing a solution  to every pro
Read more

Significant Figures With Rules in Chemistry

Image
What are Significant Figures? The reliable digits in a number that are known with the certainty are called significant figures. The last digit of measured number is generally considered uncertain by ± 1. For Example :  0.0112g contains three S.F and uncertainty is ± 0.0001 mg. 11/2mg contains three S.F and uncetainty is ± 0.1mg. The uncertainty and the number of S.F do not change when measurement is expressed in sub units. For Example: 0.0112g = 11.2mg in 0.0112g uncertainty is ± 0.0001g and in 11.2 mg uncertainty is ± 0.1mg as 0.0001g = 0.1mg. Therefore uncertainty and number of S.F do not change. Number Of Significant Figures (Digits) Depends Upon : The accurancy of the measuring instrument. The size of the object to be measured. In any series of measurements, the measured numbers are obtained to a certain degree of precision. The precision of measured is indicated by the number of significant figures. Precision : How close a series of measureme
Read more