Isotopes
Remember isotopes of an element have the same number of protons (that can NEVER change) but a different number of neutrons resulting in a different mass.
Calculating Averages
Class Average
your grade is 85% test/quiz
15% hw/lab/part
If your test average is 75 and your hw average is 100, what will your class average be?
Can they be treated equally?
Is it 87.5 or 78.75?
Calculating Average Atomic Mass
Step 1: convert % to decimal (divide by 100)
Step 2: multiply mass by decimal
Step 3: repeat for ALL isotopes and add
Class Average
your grade is 85% test/quiz
15% hw/lab/part
If your test average is 75 and your hw average is 100, what will your class average be?
Class Average
your grade is 85% test/quiz
15% hw/lab/part
If your test average is 75 and your hw average is 100, what will your class average be?
Can they be treated equally?
Is it 87.5 or 78.75?
Calculating Average Atomic Mass
Step 1: convert % to decimal (divide by 100)
Step 2: multiply mass by decimal
Step 3: repeat for ALL isotopes and add
Class Average
your grade is 85% test/quiz
15% hw/lab/part
If your test average is 75 and your hw average is 100, what will your class average be?
What is the avearge atomic mass for lithium?
Naturally occurring boron is composed of two isotopes. The percent abundance and
the mass of each isotope are listed below.
• 19.9% of the boron atoms have a mass of 10.013 atomic mass units.
• 80.1% of the boron atoms have a mass of 11.009 atomic mass units.
Is the atomic mass going to be closer to 10 or 11?
What is the average atomic mass for boron?
the mass of each isotope are listed below.
• 19.9% of the boron atoms have a mass of 10.013 atomic mass units.
• 80.1% of the boron atoms have a mass of 11.009 atomic mass units.
Is the atomic mass going to be closer to 10 or 11?
What is the average atomic mass for boron?
Mg-26 1.75 % Mg-24 98.25%
What is the average atomic mass?
What is the average atomic mass?
What is the average atomic mass for strontium?
