# Hope you had a great weekend!

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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.

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

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?

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

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?

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

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?

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

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