Page 32 - Surviving Chemistry BFF Homework Helper and Test Prep Preview

protons = atomic number = nuclear charge = electrons = mass # - neutrons = nucleons - neutrons

mass # = nucleons = protons + neutrons = nuclear charge + neutrons = electrons + neutrons

neutrons = mass # - protons = nucleons – protons

Atomic mass is the calculated average mass of all of an element’s naturally

occurring isotopes.
An
example problem and solution (steps and setup) for calculating an atomic
mass is given below.

A sample of an unknown element, X, contains the following isotopes:

80 % of X, 15% of X, and 5% of X.
65
66
64

What is the average atomic mass of element X?
(c) E3 Scholastic Publishing

Step 1 Step 2 Step 3 Step 4

(% to decimal) x (mass #) = (product) (add all products)

80% of X .80 x 64 = 51.2
64

+

15% of X .15 x 65 = 9.75 = 64.25 amu
65
+
5% of X. .05 x 66 = 3.3 atomic mass of X
66

(.80)(64) + (.15)(65) + (.05)(66) = 64.25 amu

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