Atomic Mass Agenda Review (whiteboards) Read 4.7 & 4.8 Notes Homework
Atomic MassAgenda
Review (whiteboards)Read 4.7 & 4.8 NotesHomework
Parts of Atomic Theory
How do isotopes differ?
How do ions differ?
146C
____ p+
____ e-
____ no
94Be+2
____ p+
____ e-
____ no
3617Cl-
____ p+
____ e-
____ no
READGrab bookRead section 4.7 & 4.8 w/ partner
Six inch voices
Average Atomic Massdate
Average atomic massA WEIGHTED average dependent on the
percent abundance of each isotope.If all isotopes were in a bag, how frequently
would you pull out each separate isotope.Measured in amu’s
Atomic Mass UnitAn amu is the mass of a single proton.
1 amu = 1.67*10-24 g
Determining Average MassMultiply Mass number by Percent abundance.
Add the answers.Answer should be close to most abundant isotope.
ExampleCesium is 75% 133Cs, 20% 132Cs, 5%
134Cs. What is the average atomic mass?
ExampleChromium has four istopes. 4.35% 50Cr, 83.79% 52Cr, 9.5% 53Cr, 2.36% 54Cr. What is the average atomic mass of Cr?
Determining % abundance Create an equation equaling average atomic
massMass1 * %X + Mass2 * %Y = average atomic
massCreate an equation equaling 100%
X + Y = 1Use substitution to solve for x.
Mass1 * %X + Mass2 * %(1-X) = average atomic mass
The average atomic weight of boron is 10.812amu. Boron has two isotopes: boron-10 with a mass of 10.013 and boron-11 with a mass of 11.009. What are the % abundances of each isotope?
What are the % abundances of the two isotopes of rubidium?Rb-85, 84.9918 amuRb-87, 86.9092 amu
HomeworkComplete isotopes and average atomic mass worksheet
Review scientists and discoveries.
Lab report due Rough draft WednesdayFinal draft Friday