Hope you had a great weekend!

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.

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) = • 281.73 amu

Hope you had a great weekend!