Atomic number, Mass number, Relative atomic mass and Atomic mass unit
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The document discusses atomic number, mass number, and relative atomic mass. It states that the atomic number of an element equals the number of protons in its nucleus. The mass number is the sum of protons and neutrons. An example problem finds an atom has 92 protons and 146 neutrons from a given mass number of 238 and atomic number of 92. Relative atomic mass is the average mass of an atom's isotope compared to carbon-12, measured in atomic mass units.
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Atomic number, Mass number, Relative atomic mass and Atomic mass unit
- 1. ATOMIC NUMBER (Z) Example Atomic number of Hydrogen is Z=1 atomic number of an element is equal to the number of protons present in the nucleus of its atom 1 Preparedby:QaziAbdulGhafoorSST,Govt.Boys HighSchool#1,DGKhan03321764856
- 2. MASS NUMBER (A) Mass number is the sum of the number of protons and neutrons present in the nucleus of an atom 2 Preparedby:QaziAbdulGhafoorSST,Govt. BoysHighSchool#1,DGKhan 03321764856
- 3. EXAMPLE 1.1: How many number of protons and neutrons are there in an atom having A=238, when Z=92 Solution DATA: A=238, Z=92 Number of protons =? Number of neutrons =? Number of protons =92 Number of neutrons = A-Z = 238-92 = 146 3 Preparedby:QaziAbdulGhafoorSST,Govt. BoysHighSchool#1,DGKhan 03321764856
- 4. RELATIVE ATOMIC MASS The relative atomic mass of an element is the average mass of atoms of that element as compared to 1/12th (one twelfth) of the mass of one atom of carbon-12 isotope. 4 Preparedby:QaziAbdulGhafoorSST,Govt. BoysHighSchool#1,DGKhan 03321764856
- 5. RELATIVE ATOMIC MASS EXAMPLES 1. Na has Relative Atomic Mass = 23 amu 2. O has Relative Atomic Mass = 16 amu 3. N has Relative Atomic Mass = 14 amu The unit for Relative Atomic Mass is called Atomic Mass Unit Symbol is “amu” 1 amu = 1.66 X 10-24 g 5 Preparedby:QaziAbdulGhafoorSST,Govt. BoysHighSchool#1,DGKhan 03321764856