LL Determine Avg. Atomic Mass

​LL4.2 Calculating Average Atomic Mass

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1. Atomic Structure Review

   1. Take notes as needed

2. Watch and take notes on video/ slides

3. Set up your notebook (See last slide)

​AGENDA

Atomic Structure

Atoms are made of protons, neutrons, and electrons.

The electrons are located outside the nucleus in the electron cloud.

​The nucleus is in the center of the atom and contains the neutrons and protons.

Protons carry a positive charge.

Neutrons carry no charge.

Electrons carry a negative charge.

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Atomic Structure

A closer look

An ion is a charged particle

●Different ions have the same number of

protons but different number of electrons

Anion: negatively charged ion

●Formed when atoms gain electrons
●More electrons than protons
●Nonmetals usually form anions

Anion: negatively charged ion

● Formed when atoms gain electrons
● More electrons than protons
● Nonmetals usually form anions
● Name is changed if it is a monoatomic ion (not a polyatomic) ending is changed to -ide

1. The Ion
Cations: positively charged ions

● Formed when atoms lose electrons
● More protons than electrons
● Metals usually form cations
● Name doesn't change unless roman numerals are used for the charge (Transition metals)

Multiple Select

Classify and Name

S^-2

• cation

• anion

• Name

  Sulfur(II)

• Name

  Sulfide

• Name:

  Sulfate

Multiple Select

Classify a

Mn⁺⁷

• cation

• anion

• Name

  Manganese

• Name:

  Manganese(IIV)

• Name

  Magnesium

Labelling

Label the parts of this Bohr's Model of carbon.

Drag labels to their correct position on the image

Electron Cloud

Proton

Nucleus

Neutron

Electron

Representing the Atom

A. Hyphen Notation

a. Used to represent neutral atoms
b. Ex:

i. Carbon-14
ii. Nitrogen-15
iii. Uranium-235

1. The Isotope
Isotope: two or more of the same element with
different mass numbers
● Isotopes are naturally occuring
● Different isotopes have the same number of protons

but different number of electrons

Nitrogen-14
Nitrogen-15

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Element Name

• Find this on the periodic table to find the number of protons

• Since it is a neutral atom, # of p⁺ = # of e^-

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Mass Number

• Mass # = p⁺ + n⁰

• You can use this number to find the number of neutrons in the atom (n⁰ = mass # - p⁺)

Representing the Atom

• Nuclide Notation OR Nuclear Symbol

  • Used to represent neutral atoms OR ions

  • Examples ¹⁴₆C or ⁶Li¹⁺

Mass Number
● Use this to find the

number of neutrons

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Mass Number
● Use this to find

the number of
neutrons

● Mass # = p+ + n0

Atomic Number or Element Symbol
● Tells you the number of p+

● An atomic number will not always

be listed

● If the atomic number is not listed,

look for the symbol on the PT

Charge of Ion
● Use this to find

the number of
electrons

● Charge = p+- e-

● If there is no

charge listed,
assume it is 0

Dropdown

carbon-12 has 6 protons, ​​ neutrons, and ​

Select answer

electrons.

carbon-14 has 6 protons, ​

Select answer

neutrons, and ​

Select answer

electrons.

carbon-12 and carbon-14 are ​

Select answer

Dropdown

Thorium-232 has 90 protons, ​

Select answer

​​ neutrons, and ​

Select answer

electrons.

Thorium-238 has 90 protons, ​ ​

Select answer

neutrons, and ​

Select answer

electrons.

thorium-232 and thorium-238 are ​

Select answer

​Mass Spectrometry & Average Atomic Mass

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Include

• rough drawing of the graph

• Include example problem

Multiple Choice

What do the peaks on the mass spectrum represent?

• anions
• different isotopes
• atoms with differing numbers of electrons
• numbers of electrons

Multiple Choice

What do the heights of the peaks represent in the mass spectrum?

• number of isotopes

• relative abundance of each isotope

• average atomic mass

• charge:mass ratio

Multiple Choice

How many isotopes are shown in this mass spec?

• 1

• 2

• 6

• 7

Multiple Choice

Based on the mass spec data, which Iron isotope is the most abundant?

• Fe-54

• Fe-56

• Fe-57

• Fe-58

​Set up your notebook

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LL 4.__ Lab Average Atomic Mass. Group Members:__________

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Pre-lab Discussion​: (leave about 2 inches)

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Part 1: Lab Data​ / and Calculations

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​Post Lab Questions:

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