Atomic Calculations and Mass Spectrometry
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Atomic Calculations and Mass Spectrometry. Quantum Orbital Video. Atomic Mass – Atomic Number = # Neutrons (p + n) - (p) = (n). 1 1 0. Complete the following chart: protons electrons neutrons H Zr Ca 2+ P 3- Al 3+ Cl -. 40 40 51. 20 18 20.

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1 1 0

Complete the following chart:

protons electrons neutrons

H

Zr

Ca2+

P3-

Al3+

Cl-

40 40 51

20 18 20

15 18 16

13 10 14

17 18 19


Isotopes- same atomic number but different mass

For example, there are 3 types of hydrogen atoms.

1H 2H 3H

Not all atoms of the same element are identical.


Mass Spectrometers

Are used to determine the abundance and mass of the isotopes of elements


Mass Spectrometers

A device known as a mass spectrometercan be used to determine the relative abundanceand the mass of the isotopes of elements. 

In the graph the isotopes of a sample of the element zirconium can be seen in their relative abundances.


The data can be summarized as follows:

IsotopeMass` Abundance

90Zr 90.00 amu              51.5 %

91Zr 91.00 amu               11.2 %

92Zr 92.00 amu               17.1 %

94Zr 94.00 amu               17.4 %

96Zr 96.00 amu              2.80 %

atomic mass of isotope 100 %


Calculate the weighted average mass of zirconium using the data above.

Change each percent to a decimal by dividing by 100.

Multiply by the mass.

Add it all together.

0.515(90.00)

+ 0.112(91.00)

+ 0.171(92.00)

+ 0.174(94.00)

+ 0.0280(96.00)

= 91.3 amu

3 sig figs!

Look up the mass on the periodic chart.

The unit amu describes how many times heavier than the mass of H

= 91.2 amu

They are the same with uncertainty


Calculate the average atomic mass for Germanium data above.

36.54 %

73.92115 amu

27.43 %

71.92174 amu

20.52 %

69.92428 amu

7.76 %

75.9214 amu

7.76 %

72.9234 amu

(0.2052)(69.92428) + (0.2743)(71.92174) + (0.0776)(72.9234) + (0.3654)(73.92115) + (0.0776)(75.9214) =

= 72.6 amu

Periodic Table=72.6 amu


Quantum orbitals data above.


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