Standards 1a. Students know how to relate the position of an element in the periodic table to its...

Standards1a. Students know how to relate the

position of an element in the periodic table to its atomic number and atomic mass.

1b. Students know how to use the periodic table to identify metals, semi-metals {metalloids}, non-metals, and halogens

1e. Students know the nucleus of the atom is much smaller than the atom yet contains most of its mass.

Purpose We will use this information to build our

chemistry knowledge.We will use this information as the

foundation to calculate limiting reagent problems.

The standardized exams in the spring will test you on this information.

ObjectivesKnow the 3 particles of the atom and

where they resideKnow the difference between atomic

number and mass numberKnow how to write nuclide symbolsKnow the three isotopes of hydrogenKnow how to calculate atomic massKnow how to calculate percent abundance

First Some Questions…What are atoms made up of?

Protons, Neutrons and ElectronsWhere do you find these particles?

Protons and Neutrons are located in the nucleus

Electrons are located in the outer rings, outside the nucleus.

VocabularyAtom- from the Greek atomos=indivisible. The

atom is the smallest particle of an element that retains the properties of that element.

Nucleus: the center of the atom; composed of neutrons and protons. Because the mass of the proton and the neutron is much larger than that of electrons, almost all the mass is located in the nucleus.

Ion: a charged particle; # protons ≠ # electronsElectrons occupy most of the volume of an atom

outside/around the nucleus.

Fundamental ParticlesProton

A positively charged particle located in the nucleus.

NeutronA neutral particle located in the nucleus.

ElectronA negatively charged particle located outside

the nucleus.

Animation of the Atomhttp://vvsd.schoolwires.net/2349201028132033980/lib/

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2349201028132033980/atom_animated.gif

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QuestionWhat differentiates one atom from another

atom?

The number of PROTONS

Atomic Number (Z)Number of protons in the nucleus of an

atomThis number is found on the Periodic

TableAtomic Number identifies an elementAlways a positive number (b/c it is a

counting #)Tells number of electrons in a neutral

atomAn atom is electrically neutral

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What does it mean to be electrically neutral?The atom has no chargeThe number of protons = the number of

electrons

QuestionWhat observations can you make about

atomic numbers on the periodic table?

Atomic Number increases as you go across the rows from left to right.

QuestionsWhat is the atomic number of Chlorine?

What can you tell me about its protons and electrons?

What element has 20 protons?What is the relationship between the #

protons and the atomic number? They’re equal.

Complete the ChartElement Symbol Atomic # # Protons

Potassium

5

16

Y

K 19 19

Boron B 5

Sulfur S 16

Yttrium 39 39

Atomic Structure of Potassium

Mass Number (A) Total number of protons and neutrons

in the nucleus of an atomAlways a positive numberYou can determine the nuclear

composition of an atom from its mass number and atomic number

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QuestionWhat do the atomic number and the mass

number have in common? Both Positive integersBoth have the same # of protons

How to find # of Neutrons Mass # - Atomic#= # Neutrons

Or

# protons + # neutrons= Mass # (atomic number + # neutrons)=Mass #

Complete the ChartAtomic# Mass# #Protons #Neutro

ns#Electrons

Chemical Symbol

9 10

14 15

47 22

55 25

6 C

19 9 9 F

14 29 14 Si

22 22 25 Ti

25 30 25 Mn

6 12 6 6

IsotopesAtoms of the same element with differing

numbers of neutronsAtoms with the same atomic number but

different mass numberIsotopes of an element have different massesChemical properties of different isotopes are

virtually the same

Nuclide Symbol

A=Mass #Z= Atomic #

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NuclideA specific kind of atomSpecification of an element in terms

of its nuclear composition/structureTells number of protons and number

of neutrons

# protons # neutrons # electrons

Chemical Symbol

C 6 [6, 7, 8] 6

Nuclide Symbol 6 7 6C136

Complete the ChartAtomic# Mass# #Protons #Neutro

ns#Electrons

Chemical Symbol

9 10

14 15

47 22

55 25

6 C

19 9 9 F

14 29 14 Si

22 22 25 Ti

25 30 25 Mn

6 12 6 6

Nuclide Symbol

F199

Si2914

Ti4722

Mn5525

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3 Isotopes of Hydrogen

Isotope OfHydrogen

Nuclide Symbol

# protons # neutrons # electrons

H11

H31

H21Deuterium 1 1 1

Protium 1 0 1

Tritium 1 2 1

NuclidesBy specifying the nuclear structure, then you

call it a nuclide. But if you say Carbon atom, you do not know

which Carbon atom it is, therefore you don’t know how many neutrons it has

Example: Brothers and Sisters-You are members of the Jones family, but you

have not specified which Jones member you are referring to. If you say Jimmy Jones, then we know exactly which member you are referring to. Just like when you say carbon-13, we know exactly which kind of carbon atom, the one 7 neutrons in the nucleus.

Write the nuclide name and nuclide symbol #

protons

# neutrons

# electrons

Nuclide Name

Nuclide Symbol

17 20 18

20 20 18

92 146 92

Chlorine-37Anion

Cl3717

24020Ca

U23892

Calcium-40Cation

Uranium-238

Atomic MassA weighted average of the atoms in a

naturally occurring sample of the element.Naturally occurring: no matter where you

get the sample from, it will have the same percentages of isotopes.

Construct a Fruit BasketFruit Type Weight of Each Piece

2 grapefruit 14 oz4 apples 10 oz3 pears 7 oz1 kiwi 3 oz

What is the Average Weight?

Fruit BasketAverage weight=9.2oz

Each type of fruit makes a different contribution to the overall weight

How many pieces of fruit actually weigh 9.2 ounces? None!

What does 9.2 oz mean? Fictitious non-existent piece of fruit

Atomic MassIf you have a recipe, you could count items

to put in, say 200 chocolate chips, 3 eggs, etc.

But suppose I have a recipe to make a compound. I need 100 hydrogen atoms and 50 oxygen

atoms-you cannot count atoms or pluck them out with atomic tweezers!

So instead they are massed. Careful here, the mass of an object is completely

different from the weight of an object.

QuestionWhat accounts for the mass of the atom?

# protons & # neutrons in the nucleus

Atomic MassKnow that 1.0 amu is defined as

exactly 1/12 the mass of a atom.Carbon-12 has 6 protons and 6

neutrons, therefore 1 proton or 1 neutron = ~1 amu

1 amu = 1.6606 x 10 -24 gramsSince the mass mostly depends on #

protons and # neutrons, you’d think atomic mass would be a whole number, but it isn’t. How come?

C126

Atomic Mass In nature, most elements exist as a mixture of 2 or more

isotopes. Each isotope of an element has a fixed, constant mass and

fixed constant relative abundance.Relative abundance-

The amount (%) of the isotope present in a sample of the element

Sample of carbon from anywhere in the world; coal from S. Africa, W. Virginia or Pennsylvania → 99% C-12 and 1% C-13

Atomic Mass on the periodic table takes into account the larger and smaller masses of the isotopes

→ Idea of weighted average

Calculating Atomic MassTo calculate atomic mass you need to know 3

things:# of stable isotopesMass of each isotope% abundance of each isotope

Example: Chlorine Calculationmass of isotope X relative abundance + mass of isotope X relative abundance

=_______amu

(34.969)(.7577) + (36.935)(.2423) = That’s the same value on the periodic

table!

Isotope Mass of Isotope Relative Abundance Atomic Mass

Cl-35 34.969 75.77%

Cl-37 36.935 24.23%

35.45 amu

QuestionHow many chlorine atoms actually have a

mass of 35.45 amu? NONE

So the atomic mass, in amu, is the average of a fictitious non-existent atom of an element.

Example: Copper CalculationIsotope Mass of Isotope Relative Abundance Atomic Mass

Cu-63 62.9298amu 69.09%

Cu-65 64.9278 30.91%

(62.9298)(.6909)+(64.9278)(.3091)=63.5464 amu

Calculating Relative AbundanceTo Calculate % Abundance:

Make a ChartIsotopic Mass x % Abundance of each

isotopeSet-up equationSolve for “x” Plug in “x” value to solve for “y”

ExampleIsotope Mass of Isotope Relative Abundance Atomic Mass

B-10 10.013

B-11 11.009

1.00x + y = 1.00y = 1 – x

10.013 (x) + 11.009 (1 –x) = 10.811

10.013x + 11.009 -11.009x = 10.811

-0.996x = -0.198x = .1987

y= 1-.1987 y= .8013

B-10 = 19.87%

B-11 = 80.13%

x

1- x

The End