Percent Abundance Chemistry

Isotopes

What are isotopes and isotopic notation and how do you calculate the average atomic mass?

Isotopes 

• Same protons(atomic number) and electrons (so neutral)

• Have different number of neutrons so different mass numbers

• Are defined as different percents of the total average atomic mass

• Often are presented as isotopic notation

Writing and defining isotopic notation

How to translate isotopic notation

Open Ended

Give the protons, neutrons, and electrons for the following isotopic notation of silicon(Si)

²⁹ ₁₄ Si

Open Ended

Give the isotopic notation for atomic number 10 neon (Ne-21)

How do I determine the average atomic mass?

• multiply the atomic mass given for the isotope by its' given percent abundance 

• add this to the next isotopes given atomic mass times its' given percent abundance

• then divide by 100.

• The formula in the video converts each percent to decimal form first, this is another way to do these problems

Open Ended

Calculate the average atomic mass of hydrogen given the following

² ₁H is 0.05% abundance and

¹₁H ^is 98.95 % abundance

Open Ended

Which isotope of chlorine has the higher percent abundance given that the periodic table says the average atomic mass of chlorine is 35.45 amu

³⁵ ₁₇Cl or ³⁴₁₇Cl