Learning Log Objectives

• Be able to create isotope notation and identify the number of subatomic particles

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• Calculate the average atomic mass of an element

Isotopes

• Isotope: atoms with same number protons and differing neutrons

Isotopes

• All atoms of an element are considered an isotope, only some are more common than others.

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Isotopes

• Atomic mass is the average of all isotopes of the element.
• To find the most common isotope round the atomic mass to nearest whole number.

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Isotopes

Which isotope is the most common for the element Boron?

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Which particle in the picture below remains constant between the different isotopes?

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Which particle is different?

Why is Carbon-14 in Red?

• Carbon-14 is an unstable isotope and decays as time goes on. That’s why caron-14 is used to date objects.
• Unstable isotopes called radioisotopes undergo changes and release energy to become more stable.

Isotope Notation

C

14

6

Mass number →

Atomic number →

12

6

How many protons and neutrons does carbon-12 have?

Isotope Notation

C

14

6

Mass number →

Atomic number →

13

6

How many protons and neutrons does carbon-13 have?

Isotope Notation

N

14

6

Mass number →

Atomic number →

14

7

How many protons and neutrons does nitrogen-14 have?

Create the correct Isotope Notation for the following elements

Example: 1 Proton 1 Neutron= ²₁H

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1. 8 Protons 10 Neutrons

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• 22 Protons 23 Neutrons

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Create the correct Isotope Notation for the following elements

Example: 1 Proton 1 Neutron= ²₁H

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• 82 Protons and 125 Neutrons

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• 25 Protons and 82 Neutrons

How many protons are in one atom of Calcium?

Write the isotope notation for Calcium for the most common isotope?

How does Nitrogen-14 differ from Nitrogen-13?

What is the atomic number of Iron-56?

Write the isotope notation for Iron-56

What is the mass number of an element with 41 protons and 51 neutrons?

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Write the isotope notation for this isotope

An element with an atomic number of 88 and an atomic mass of 226 has how many neutrons?

Pre-AP

What is an Ion?

• Ion: An atom that has lost or gained one or more electrons, giving the atom a new positive ( + ) or a negative( -- ) charge.

Isotope Notation with charges

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How many protons? How many neutrons?

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How many electrons?

Isotope Notation

C

14

6

Mass number →

Atomic number →

12

6

How many protons and neutrons does carbon-12 have?

+3

How many electrons does carbon-12 have?

Isotope Notation

C

14

6

Mass number →

Atomic number →

13

6

How many protons and neutrons does carbon-13 have?

+4

How many electrons does carbon-13 have?

How many Protons, Neutrons and Electrons?

Determine the number of electrons for the following isotopes

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Isotope Exit Ticket

Calculating Average Atomic Mass

Atomic mass is a calculation of the mass of an element, when taking into account All the naturally occurring isotopes.

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Each isotope shares the same number of protons and electrons AND they have varying numbers of neutrons.

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All Elements have isotopes

Hydrogen H - 3 isotopes

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Potassium K - 3 isotopes

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Uranium U - 2 isotopes

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Tin - 10 Isotopes

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Iron Fe - 2 Isotopes

The number of actual Isotopes found in nature is NOT the same for all isotopes!

If you were to go hunting for an isotope, you would want to know, what is your percent chance of finding one.

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Percent abundance describes the percent amount (how much) this isotope exists in nature.

17 = _____ X 100 =

18

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1 = _____ X 100 =

18

• The Overall Abundance must equal 100% in order to represent all isotopes found in nature

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• Every Isotope is an atom of the same element
• The Overall Abundance must equal 100% in order to represent all isotopes found in nature

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Calculating Average Atomic Mass:

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1. Convert abundance into decimal form

Calculating Average Atomic Mass

Step 1

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Step 2

Combine the average atomic mass with the decimal

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107 Ag ( ) X 106.90509

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109 Ag ( ) X 108.90470

Calculating Average Atomic Mass�Step 3

Use this equation

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Average Atomic Mass =

(mass of isotope 1 X decimal abundance) + (mass of isotope 2 X decimal abundance)

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(106.9 X 0.5186) + ( 108.9 X 0.4814) =

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Add units →

WE DO:

Calculate the average Atomic Mass

Boron has two naturally occurring isotopes.

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Calculate the average atomic mass of boron.

You do:

#1 Calculate the average atomic mass of magnesium, Mg.

WE DO

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Thallium has two stable isotopes, thallium-203 and thallium-205. Thallium-203 has an atomic mass of 202.9723 amu and a percent abundance of 29.52%. Thallium-205 has an atomic mass of 204.9744 amu and a relative abundance of 70.48%. What is the average atomic mass of thallium?

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Question 2

Silicon has two stable isotopes. Silicon-28 has an atomic mass of 27.976 amu and a percent abundance of 92.23%. Silicon-29 has an atomic mass of 28.976 amu and a percent abundance of 4.67%. Calculate the average atomic mass of silicon.

Challenge

Look up the atomic mass of neon on the periodic table.

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Why is this atomic mass a decimal, not an integer?

Pre-AP We Do

Examine the following isotopic composition information:

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1. What is the atomic mass of Neon 22 if the average atomic mass of Neon is 20.1797 amu?

Pre-AP Question 3

Calculate the atomic mass of Martorium-25 (Mt) if the average atomic mass is 24.443 amu. (FYI this is a fake element)