Name: _____________________________________________ Date: ___________________ Period: ________
Isotope PPT note taking guide
1. Protons define the element
 _______________ that have the _______________ number of _______________ are
_______________ atoms of a _______________ element.
2. Neutrons can vary
 BUT _______________ can have _______________ numbers of _______________ and still be an
_______________ of a _______________ element.
3. Isotopes
 This is because _______________ can have _______________ (basically _______________ of the
same element with a _______________ number of _______________ in their _______________).
4. Dalton was wrong
 When Dalton stated his atomic theory in the early 1800’s, he _______________ that all of the
atoms of a given element were _______________.
5. James Chadwick
 Over 100 years after Dalton, James Chadwick _______________ that the _______________ of
most _______________ contains _______________ as well as
protons.
6. Dalton’s Theory Changes
 Dalton’s theory now states:
- All atoms of the same element contain the same number of protons and electrons, but
atoms of a given element may have different numbers of neutrons.
7. The Isotopes of Hydrogen

Hydrogen – 1
- Also written _______________
- Also known as _______________
- Hydrogen has an _______________ _______________ of _____, so it has _____ proton
- The hyphen notation above tells us that the mass number of H-1 is _____
o Number of neutrons = mass number – atomic number
o So H-1 must have _____ neutrons
 Hydrogen – 2
- Also written _______________
- Also known as _______________
- Hydrogen has an _______________ _______________ of _____, so it has _____ proton
- The hyphen notation above tells us that the mass number of H-2 is _____
o Number of neutrons = mass number – atomic number
o So H-2 must have _____ neutron
 Hydrogen – 3
- Also written _______________
- Also known as _______________
- Hydrogen has an _______________ _______________ of _____, so it has _____ proton
- The hyphen notation above tells us that the mass number of H-3 is _____
o Number of neutrons = mass number – atomic number
o So H-3 must have _____ neutron
8. Calculate the number of neutrons
 For chlorine found on the periodic table (the most common form of chlorine that is found in
nature) Chlorine-35
 For Chlorine-37
 Chlorine-35 = _____ neutrons, Chlorine-37 = _____ neutrons
 For Cobalt found on the periodic table Cobalt-59
 For Cobalt-60
 Cobalt-59 = _____ neutrons, Cobalt-60 = _____ neutrons
9. Calculating Average Atomic Mass
 Average _______________ mass is the atomic _______________ that _______________ on the
_______________ table.
For example –

Copper has an _______________ atomic _______________ of _______________ amu.
Yet, in _______________, most elements are _______________ as _______________ of two or more
_______________. For example, copper consists of

69.17% copper-_____ which has a _______________ atomic _______________ of 62.94 amu
AND

30.83% copper-_____ which has a _______________ atomic _______________ of 64.93 amu
To find the _______________ atomic _______________, multiply the _______________ equivalent of
the _______________ (for example 69.17% = 0.6917) of each _______________ by the respective
_______________ atomic _______________ and _______________ the _______________.
Isotope
Copper – 63
Copper – 65
Relative abundance in nature
Relative atomic mass
(_______________ X _______________) + (_______________ X _______________) = 63.55 amu
10. Practice Calculating Average Atomic Mass
 Boron – _____ is _______________ 19.9% of the _______________ in _______________ and has a
_______________ atomic _______________ of 10.013 amu
 Boron – _____ is _______________ 80.1% of the _______________ in _______________ and has a
_______________ atomic _______________ of 11.009 amu
 Calculate the _______________ _______________ _______________ of Boron
Isotope
Boron – 10
Relative abundance in nature
Relative atomic mass
(_______________ X _______________) + (_______________ X _______________) =
Boron – 11
11. Practice Calculating Average Atomic Mass

Magnesium – _____ is _______________ 78.99% of the _______________ in _______________
and has a _______________ atomic _______________ of 23.985042 amu

Magnesium – _____ is _______________ 10.00% of the _______________ in _______________
and has a _______________ atomic _______________ of 24.985837 amu

Magnesium – _____ is _______________ 11.01% of the _______________ in _______________
and has a _______________ atomic _______________ of 25.982593 amu

Calculate the _______________ _______________ _______________ of Magnesium
Isotope
Magnesium – 24
Magnesium – 25
Magnesium – 26
23.985042 amu
24.985837 amu
25.982593 amu
Relative abundance in nature
Relative atomic mass
(_______________ X 23.985042) + (_______________ X 24.985837) + (_______________ X 25.982593) =