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0. Isotopes. 0. A quick review of the atom. completely different atom. Identity of the atom. Charge. Ion. Mass. Isotope. They are atoms of the same element that have different numbers of neutrons. 0. What Are Isotopes ?. It ’ s just a change in the neutrizzle fo shizzle!!!.

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0

Isotopes


A quick review of the atom

0

A quick review of the atom

completely different atom

Identity of the atom

Charge

Ion

Mass

Isotope


What are isotopes

They are atoms of the same element that have different numbers of neutrons.

0

What Are Isotopes?

It’s just a change in the neutrizzle fo shizzle!!!


An example

Hydrogen has 3 numbers of isotopes

There are 3 different “versions” of a hydrogen atom

0

An Example

Note how the number of

protons never change!!!


An example1

Hydrogen has 3 numbers of isotopes

There are 3 different “versions” of a hydrogen atom

0

An Example

Having more neutrons

increases the mass


An example2

Hydrogen has 3 numbers of isotopes

There are 3 different “versions” of a hydrogen atom

0

An Example

Mass number = 1

Mass number = 3

Mass number = 2


Why does the atomic mass on the periodic table have so many decimal places

0 numbers of

Why does The atomic mass on the periodic table have so many decimal Places?

6

C

12.01115

13

Al

26.982

10

Ne

20.180


Atomic mass

0 numbers of

Atomic mass

1

H

1.00797

This atomic mass is the one number that best represents the mass of all three versions of hydrogen.


Atomic mass1

0 numbers of

Atomic mass

1

H

1.00797

No atom of hydrogen anywhere in the universe actually has this mass.


Atomic mass2

0 numbers of

Atomic mass

1

H

1.00797

This number is a “weighted” average of the masses of every isotope of hydrogen


Calculating a weighted average

1. First, you have to know the numbers of mass of each isotope

2. Second, you have to know the percent abundance*of each isotope

*see next slide

0

Calculating a “weighted” average


Percent abundance

Percent abundance numbers of is how often that particular isotope occurs in a sample of the element

0

Percent abundance?

A sample of magnesium collected anywhere in the universe will contain three isotopes of magnesium.

Sample of Magnesium


Percent abundance1

These are the percent abundances of each isotope of magnesium

0

Percent abundance?

78.90% of this magnesium will be the isotope named “magnesium 24”

10.00% of this magnesium will be the isotope named “magnesium 25”

Sample of Magnesium

11.10% of this magnesium will be the isotope named “magnesium 26”


Percent abundance2

This data will be provided to you in problems or you will be given a table where you can look it up.

0

Percent abundance?

78.90% of this magnesium will be the isotope named “magnesium 24”

10.00% of this magnesium will be the isotope named “magnesium 25”

Sample of Magnesium

11.10% of this magnesium will be the isotope named “magnesium 26”


Calculating a weighted average1

The formula given a table where you can look it up.

(Mass of isotope #1)(percent abundance)

100

(Mass of isotope #2)(percent abundance)

100

(Mass of isotope #3)(percent abundance)

100

0

Calculating a “weighted” average


Calculate the atomic mass of magnesium from the given data

0 given a table where you can look it up.

Calculate the atomic mass of magnesium From the given data


Calculating the atomic mass of magnesium

Using the formula for calculating a weighted average given a table where you can look it up.

23.985045(.7890)

+24.985839(.1000)

+25.982595(.1110)

24.306852 amu’s

0

Calculating the Atomic mass of magnesium

Since its a “weighted”

average this number

has more influence since

this mass occurs 79% of

the time

It’s NOT just a straight

average where you add

the masses and divide

by 3

Note how the %

abundances were

converted to decimals

(just divide each by 100)


Try another example
Try another example… given a table where you can look it up.


Calculate the atomic mass of chromium

0 given a table where you can look it up.

Calculate the Atomic Mass of Chromium


Calculate the atomic mass of chromium1

49.946046( given a table where you can look it up.0.0435)

51.940510(0.8379)

+ 52.940651(0.0950)

53.938882(0.0236)

51.995926 amu’s

0

Calculate the atomic mass of chromium


Terms associated with isotopes

0 given a table where you can look it up.

Terms associated with isotopes

Vocabulary review


Vocabulary review

Atomic number given a table where you can look it up. = the number of protons

  • It’s the same as the element’s position on the periodic table

  • For example, carbon is the 6th element on the table, so its atomic number is 6 which means it has 6 protons (and 6 electrons if it’s a neutral atom)

0

Vocabulary review


Vocabulary review1

Atomic mass given a table where you can look it up. = the “weighted” average mass of all the different isotopes of an atom

  • This is the “weird” number on the periodic table that usually has a bunch of places past the decimal point

0

Vocabulary review


Vocabulary review2

Mass number given a table where you can look it up. = the sum of protons + neutrons

  • This one kind of makes sense because the electrons essentially don’t have any mass

  • This HAS to be a whole number because you can’t have part of a proton or neutron

  • Mass number is NOT given on the periodic table

0

Vocabulary review


Let s practice those terms

  • What is the mass number of a carbon atom that has 6 neutrons? 7 neutrons?

  • How many neutrons does a nitrogen atom have if its mass number is 14?

  • How many neutrons does a chlorine atom have if its mass number is 36?

  • What is the atomic number of neon?

  • What is the atomic mass of neon?

0

Let’s Practice Those Terms…


Answers

  • 12 and 13 neutrons? 7 neutrons?

  • 7

  • 19

  • 10

  • 20.180 amu’s

0

Answers


A shorthand way to write isotopes

0 neutrons? 7 neutrons?

A shorthand way to write isotopes

AXZ Notation for Isotopes


A short way to write isotopes

A neutrons? 7 neutrons?XZ

0

A Short Way to Write Isotopes

“A” is the symbol

for Mass Number

(#protons + #neutrons)

“Z” is the

symbol for

Atomic Number

(# of protons)

“X” will be the

symbol of the element


Jay z
Jay - Z neutrons? 7 neutrons?

Yo! If you’re doin’ chem problems I feel bad for you son….

I got 99 problems, and here’s the first one….HIT ME!!!!


Problem 1

Write neutrons? 7 neutrons?aXz notation for an isotope that has 17 protons and 18 neutrons.

Problem #1


Problem 11

Write neutrons? 7 neutrons?aXz notation for an isotope that has 17 protons and 18 neutrons.

35Cl17

Problem #1


Problem 2

Write neutrons? 7 neutrons?aXz notation for an isotope that has 19 protons and 21 neutrons.

Problem #2


Problem 21

Write neutrons? 7 neutrons?aXz notation for an isotope that has 19 protons and 21 neutrons.

40K19

Problem #2


Problem 3

Write neutrons? 7 neutrons?aXz notation for an isotope that has 15 protons, 18 electrons, and 16 neutrons.

Problem #3


Problem 31

Write neutrons? 7 neutrons?aXz notation for an isotope that has 15 protons, 18 electrons, and 16 neutrons.

31P3-15

Problem #3

This isotope is

also an ion!!!



Problem 41

How many protons, electrons, and neutrons are in this isotope?

41Ca2+ 20

20 protons, 18 electrons, 21 neutrons

Problem #4


More examples

How many protons, electrons, and neutrons? isotope?

  • 56Fe2+26

  • 27Al3+13

  • 79Se2-34

More examples


More examples1

How many protons, electrons, and neutrons? isotope?

  • 56Fe2+26 26, 24, 30

  • 27Al3+13 13, 10, 14

  • 79Se2-34 34, 36, 45

More examples


More practice

Write aXz notation for: isotope?

  • Isotope with 21 protons, 18 electrons, and 24 neutrons

  • Isotope with 53 protons, 74 neutrons, and 54 electrons

More practice


More practice1

Write aXz notation for: isotope?

  • Isotope with 21 protons, 18 electrons, and 24 neutrons

    45Sc3+21

  • Isotope with 53 protons, 74 neutrons, and 54 electrons

    127I-53

More practice


Different forms of a x z

35 isotope?Cl17 is the same as 3517Cl

Might also see “Cl-35” or “chlorine-35”

Different Forms of AXZ


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