1. Mr. Anthony Gates AP Chemistry Unit 9
Mass Spectroscopy
Mr. Anthony Gates
AP Chemistry
Unit 9

3. Isotopes
Isotopes: atoms of the same element with different masses due to varying amounts of neutrons.
Isotope
Protons
Electrons
Neutrons
Nucleus
Hydrogen-1
(Protium) 1
Hydrogen-2
(Deuterium)
Hydrogen-3
(Tritium) 2

4. Composition of the Nucleus
Atomic Mass
Atomic mass is the average of all the naturally occurring isotopes of that element.
Carbon = g/mol
Isotope
Symbol
Composition of the Nucleus
% in Nature
Carbon-12
12C
6 protons
6 neutrons
98.89%
Carbon-13
13C
7 neutrons
1.11%
Carbon-14
14C
8 neutrons
<0.01%

5. Mass Spectrometry

6. Mass Spec. cont.
Data from mass spectrometry aka. mass spectroscopy demonstrate evidence that an early model of the atom (Dalton’s model) is incorrect; these data then require a modification of that model.
Data from mass spectrometry also demonstrate direct evidence of different isotopes from the same element.
The average atomic mass can be estimated from mass spectra.

8. Atomic Mass Isotope Isotopic mass (amu) Abundance (%) 6329Cu 62.9298
69.09
6529Cu
30.91
Atomic mass is then calculated in the following way:
( )(0.6909) =
( )(0.3091) =
63.55

9. Mass Spectrum of CO2

10. Mass Spectrum of Bromine Bromine has two isotopes: 50
Mass Spectrum of Bromine Bromine has two isotopes: 50.69% Bromine-79 and 49.31% Bromine-81

11. Methyl Bromide CH3Br

12. Methylene Chloride (CH2Cl2) Chlorine is 75.77% 35Cl and 24.23% 37Cl

13. Vinyl Chloride (CH2CHCl) Chlorine is 75.77% 35Cl and 24.23% 37Cl