1. Hope you had a great weekend!
Test on Friday – Start studying a little each night.
Isotopes are atoms of the same element with different numbers of _________ which results in different _______ numbers.
What are three isotopes of Hydrogen?
When you’re done with the warm-up, look over the element math worksheet from last Thursday because we’re going to start class with a quiz.

2. Unit Two, Day Three Kimrey 10 September 2012
Chemistry!!
Unit Two, Day Three
Kimrey
10 September 2012

3. Suppose that there were two isotopes of Sodium.
28% of the naturally occurring sodium atoms had a mass of 22,
and 72% atoms had a mass of 23.
What would the average atomic weight of sodium be?

4. 28% = .28
72% = .72
(.28 x 22 ) + (.72 x 23 ) =
22.72 amu

5. Suppose that there were two natural isotopes of Copper.
80% of the atoms had a mass of 63,
and 20% of the atoms had a mass of 65.
What would the average atomic weight of copper be?

6. 80% = .80
20% = .20
(.80 x 63) + (.20 x 65) =
63.4 amu

7. Suppose that a new element (E) were discovered that existed as three natural isotopes.
25% of the atoms had a mass of 278,
38% had a mass of 281,
and the remainder had a mass of 285.
What would be listed as the atomic weight of this element?

8. 25% = .25
38% = .38
100% - (25% + 38%)
37% = .37
(.25 x 278) + (.38 x 281) + ( .37 x 285) =
amu