DAY 1: ATOMIC STRUCTURE & AVERAGE ATOMIC MASS



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|UNIT 2: Atomic Theory and Structure |

|Part A: History and Structure of the Atom |

|Part B: Nuclear Chemistry |

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|Big Picture Ideas: |

|The development of the current atomic model directly correlated with advancements in technology. |

|An element’s electronic structure determines its chemical and physical properties. |

|Radioactivity results from an imbalance of forces in the nucleus. |

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|Big Picture Questions: |

|o How did the advancements in science/technology help to develop the current atomic model? |

|How does an element’s electronic structure affect its properties? |

|What factors determine the stability of an atom? |

|Suggested Resources… |

|Homework Assignments |

|Classwork Assignments |

|Laboratory Activities |

|Formative Assessments |

|Textbook pages: Chapters 3 & 24 |

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|Key Terms: |

|atom |

|law of definite composition |

|nucleus |

|proton |

|neutron |

|atomic mass unit |

|atomic number |

|ion |

|isotope |

|mass number |

|atomic mass |

|mole |

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|Democritus |

|Dalton |

|Thomson |

|Rutherford |

|Millikan |

|cathode ray tube |

|nuclear reactions |

|radioactive decay |

|alpha particle |

|beta particle |

|gamma ray |

|24. half-life |

|Directions: Use this information as a general reference tool to guide you through this unit. Don’t hesitate to ask your teacher for help! |

|By the conclusion of this unit, you should know the following: |By the conclusion of this unit, you should be able to do the |

| |following: |

|The contributions made by Dalton, Thompson, Rutherford, and Millikan in the | |

|development of the current atomic model. |Compare and contrast the different atomic models. |

|Define atom, the different subatomic particles that compose it, and how |Determine numbers of protons, neutrons, and electrons in an |

|differences in numbers of these subatomic particles lead to ions or isotopes. |atom or ion given its isotopic notation. |

|Atomic masses are weighted averages based on the different isotopes that exist. |Calculate average atomic mass. |

|The gram atomic mass of an element is the mass of one mole of the element. |Determine the number of moles or atoms in a given mass of an |

|The number of atoms in a given mass of an element can be calculated using the gram|element. |

|atomic mass. |Calculate the number of atoms in a given mass of an element. |

|Unstable nuclei lead to radioactive decay. |Write nuclear reactions based on the type of radioactive |

|The identity of an atom can be changed through fission or fusion reactions. |decay. |

|Radioactive decay (half-life) occurs at a predictable rate and therefore can be |Calculate half-life based on data. |

|used to date materials. | |

Practice Problems:

1. Gold foil experiment: what did it prove, how did he prove it?

2. What is the law of constant composition?

3. What is static electricity? What causes it?

4. Dalton’s 4 statements to his atomic theory.

5. What is the difference between atomic number, mass number, and atomic mass? What information do we know about the atom from these numbers? Which number specifies an atom of an element?

6. Diagram how these scientists formed their idea (and what the idea was) of the atom: Democritus, Thomson, Rutherford, Bohr, Millikan.

7. What is the difference between an atom and an ion? How do they change from one to another- what does the charge mean?

8. What is a cathode ray tube? What is an anode/cathode? What is the cathode ray made of? In what direction did it travel in the tube? What happens to the ray when a negative charge is brought near it?

9. Write the isotopic notation:

a) 40p, 49 n, 40 e b) 56 p, 85n, 54e c) 33 p, 40 n, 36e

10. Given the following tell the # of protons, neutrons, and electrons:

59 28Ni +2 119 50Sn 32 16 S -2 85 37Rb

11. Silver has two isotopes. One has a mass of 106.905 amu (52.00%) and one has a mass of 108.905 (48.00%). Calculate its atomic mass.

12. Fill in table:

|Atomic # |Mass # |# of protons |# of neutrons |# of electrons |charge |

|15 | | | |18 | |

| |37 |20 | | |0 |

| | | |26 |18 |+3 |

|45 | | |58 | |+1 |

| |127 |52 | | |-2 |

13. Find the mass of 0.5 moles of sulfur. 14. How many atoms is 275g of barium?

Name Date Class

DEFINING THE ATOM

Section Review

Objectives

• Describe Democritus’s ideas about atoms

• Explain Dalton’s atomic theory

• Describe the size of an atom

Vocabulary

|atom |

|Dalton’s atomic theory |

Part A Completion

Use this completion exercise to check your understanding of the concepts and terms that are introduced in this section. Each blank can be completed with a term, short phrase, or number.

Elements are composed of tiny particles called _______ Atoms of any one element are _______ from those of any other element. Atoms of different elements can form _______ by combining in whole-number ratios. Chemical reactions occur when atoms are _______.

1.

2.

3.

4.

Part B True-False

Classify each of these statements as always true, AT; sometimes true, ST; or never true, NT.

5. Atoms of one element change into atoms of another element during chemical reactions.

6. Atoms combine in one-to-one ratios to form compounds.

7. Atoms of one element are different from atoms of other elements.

Chapter 4 Atomic Structure 83

Name Date Class

Part C Matching

Match each description in Column B to the correct term in Column A.

Column A

8. atom

9. scanning tunneling microscope

10. John Dalton

11. Democritus

Column B

a. an instrument used to generate images of individual atoms

b. Greek philosopher who was among the first to suggest the existence of atoms

c. the smallest particle of an element that retains its identity in a chemical reaction

d. English chemist and schoolteacher who formulated a theory to describe the structure and chemical reactivity of matter in terms of atoms

Part D Questions and Problems

Answer the following questions in the space provided.

12. In what type of ratios do atoms combine to form compounds?

13. How many copper atoms would you have to line up side by side to form a line 1 m long?

Historical Development of our Model of the Atom

1. Your group will be assigned a scientist to research. Use the textbooks available in class to read about your scientist and find the:

1. Scientist’s Name:

2. Time frame/Location of his work:

3. Describe his main contribution to the Modern Atomic Theory: If your scientist is associated with a particular model of the atom – include it. Otherwise, describe his contribution to our understanding of atomic structure

4. Draw a picture of the model (only if your scientist is associated with a particular model of the atom)

5. Draw or describe any significant experiment he did.

6. Dalton – list all components of his atomic theory.

2. Your group is responsible for teaching the class about your scientist. Your presentation must include the information above.

In addition, chose one of the following formats to help the class learn about your scientist:

1. a poem or limerick

2. a song (put your information to the tune of a song)

3. a cartoon

4. an acrostic

SCIENTISTS: John Dalton, J. J. Thomson, Ernest Rutherford, Niels Bohr

Dalton – atomic theory

Thomson – experiment, model & main contribution

Rutherford – experiment, model & main contribution

Bohr – model & main contribution

SCIENTIST NOTES

|NAME |CONTRIBUTION |MODEL OR EXPERIMENT |

| |Atomic Theory: |Solid Sphere – “Billiard Ball Model” |

| |All matter is made of atoms (atoms are indivisible and |-different atoms were drawn at different sizes |

|JOHN DALTON |indestructible) |[pic] |

| |All atoms in an element are identical to each other in mass | |

| |and properties | |

| |Compounds are formed by a combination of 2 or more different | |

| |kinds of atoms in different ratios | |

| |A chemical reaction is a rearrangement of atoms | |

| |In reactions, matter is neither created or destroyed (law of | |

| |conservation of matter) | |

| |Discovered electrons |- Negative electrons set in a sponge of “+” charge |

| |Used cathode rays to show how electrons were deflected by |-“Cookie Dough” Model |

|J. J. THOMSON |magnetic forces |[pic] |

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| |Gold Foil experiment – proved nuclear form |“Nuclear” Model |

| |Discovered a positively charged nucleus (99.9% of mass of |Protons in nucleus with electrons floating outside |

|ERNEST RUTHERFORD |atom) |nucleus |

| |Atoms are mostly made up of empty space | |

| | |[pic] |

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|NIELS BOHR |Discovered electron motion |“Solar System” Model |

| |Said that electrons orbit around the nucleus |[pic] |

| |Light emissions (next chapter!) | |

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ATOMIC STRUCTURE & AVERAGE ATOMIC MASS

|PARTICLE |LOCATION |CHARGE |MASS |RELATIVE MASS |

|proton |NUCLEUS |+ |1.6 X 10 -24 g |1 atomic mass unit (amu) |

|neutron |NUCLEUS |NEUTRAL |1.6 X 10 -24 g |1 amu |

|electron |ELECTRON CLOUD |- |9.1 X 10 -28 g |0 amu |

Atom – smallest particle of an element that retains its identity in a chemical reaction

An atom is __neutral______________, which means that the # of protons (p+) = # of electrons (e-)

Periodic Table “Box”

[pic]

atomic number – NUMBER OF PROTONS IN NUCLEUS OF THE ATOM; IDENTIFIES THE ELEMENT

atomic mass – PROTONS AND NEUTRONS: WEIGHTED AVERAGE OF MASS OF ALL ISOTOPES OF AN ELEMENT

atomic mass number – ATOMIC MASS ROUNDED TO THE WHOLE # = PROTONS + NEUTRONS

|ELEMENT |SYMBOL |ATOMIC |ATOMIC |PROTONS |NEUTRONS |ELECTRONS |

| | |NUMBER |MASS # | | | |

| |Na |11 |23 |11 |12 |11 |

|Sodium | | | | | | |

|Iron |Fe |26 |56 |26 |30 |26 |

|BARIUM |Ba |56 |137 |56 |81 |56 |

|SILVER |Ag |47 |108 |47 |61 |47 |

|CHROMIUM |Cr |24 |52 |24 |28 |24 |

|BROMINE |Br |35 |80 | |45 |35 |

| | | | |35 | | |

|TIN |Sn |50 |119 |50 |69 |50 |

SCIENTIFIC (EXPONENTIAL) NOTATION

Scientific notation uses powers of ten to express very large or very small numbers.

Numbers expressed in scientific notation have a single digit, followed by a decimal and the remainder of the digits. The number is then multiplied by a power of ten. The exponent is determined by the number of times the decimal must move to be in this position. Numbers greater than one have a positive exponent, and numbers between zero and one have a negative exponent.

Example: 5,450g = 5.450 x 103g 0.00027 = 2.7 x 10-4g

TRY: CONVERT BETWEEN SCIENTIFIC NOTATION AND STANDARD NOTATION:

TRY: CONVERT BETWEEN SCIENTIFIC NOTATION AND STANDARD NOTATION:

a. 465mL = __4.65x102______________ mL g. 0.000 000 000 440 mg = __4.4x10-10________mg

b. 69,755g = __6.9775x104____________ g h. 5.50 x 103 L = ___5,500___________________L

c. 234,241 J = __2.34241x105__________J i. 2.75 x 106 J = ___2,750,000________________J

d. 750,000,000,000g = _7.5x1011_______g j. 3.5 x 10-2 cal = ___0.035__________________cal

e. 0.0125 cm3 = __1.25x10-2___________cm3 l. 2.29 x 10-6 g = ___0.00000229_____________g

f. 0.000086 kPa = ___8.6x10-5_________kPa

On many calculators, the power of ten is written as E or EE, or the exponent is separated from the rest of the numbers. Try dividing one by 500,000,000 (1 ÷ 500,000,000) on your calculator. What do you see?

_____2 E -9__________________. This can be rewritten as _____2x109_____________________ or

__0.000000002____________________.

TRY: CONVERT THE F0LLOWING CALCULATOR READINGS TO SCIENTIFIC AND STANDARD NOTATION

a. 2.45 E3 ___2.45x103________________________ c. 9.78 E-2 ____9.78x10-2______

b. 1.40 05 ___1.4x105________________________ d. 3.9 -04 ____3.9x10-4________

ENTERING NUMBERS IN SCIENTIFIC NOTATION INTO YOUR CALCULATOR: To enter numbers into your calculator in scientific notation, use the EE or EXP key on your calculator. Enter the base number, then EE or EXP, followed by the exponent. DO NOT USE THE 10^ KEY! (on the graphing calculator, the EE is shift ,)

TRY: ENTER THE FOLLOWING QUANTITIES INTO YOUR CALCULATOR:

a. 4.51 x 1021 b. 9.86 x 10-13

ELEMENTS, ISOTOPES & IONS

isotope: Forms of an element with the same atomic #, but different atomic mass

isotope notation: carbon -14 C-14 14C

ion: charged particles (# of protons does NOT equal # of electrons)

Ca2+ O2-

|ELEMENT |SYMBOL |ATOMIC |ATOMIC |PROTONS |NEUTRONS |ELECTRONS |

| | |NUMBER |MASS # | | | |

| |Mg |12 |24 |12 |12 |12 |

|magnesium | | | | | | |

| | |50 |119 |50 |69 |50 |

|Tin |Sn | | | | | |

|Strontium | |38 |88 |38 |50 |38 |

| |Sr | | | | | |

|titanium | |22 |48 |22 |26 |22 |

| |Ti | | | | | |

| |Ba-140 |56 |140 |56 |84 |56 |

|barium-140 | | | | | | |

| |Pb-210 |82 |210 |82 |128 |82 |

|lead-210 | | | | | | |

|Cobalt – 60 | |27 |60 |27 |33 |27 |

| |60Co | | | | | |

|Uranium-240 | |92 |240 |92 |148 |92 |

| |240U | | | | | |

|Oxygen-17 |O-17 | |17 |8 | |8 |

| | |8 | | |9 | |

|Arsenic-78 |78As |33 |78 | | |33 |

| | | | |33 |45 | |

|Potassium-40 |40K |19 |40 | | |19 |

| | | | |19 |21 | |

|magnesium ion | |12 |24 |12 |12 |10 |

| |Mg2+ | | | | | |

| | |13 |27 |13 |14 |10 |

|aluminum ion |Al3+ | | | | | |

| | |7 |14 |7 |7 |10 |

|nitride ion |N3- | | | | | |

| | |9 |19 |9 |10 |10 |

|fluoride ion |F1- | | | | | |

| |Rb+1 | |85 |37 |48 | |

|XXXX | |37 | | | |36 |

| |S-2 | |32 |16 |16 | |

|XXXX | |16 | | | |18 |

PRACTICE: Complete the following chart.

|Element/Ion |Atomic Number |Atomic Mass |Mass Number |Protons |Neutrons |Electrons |

|[pic] |1 | |1 |1 |0 |1 |

|Lithium |Li |3 |7 |3 |4 |3 |

|Lead |Pb |82 |207 |82 |125 |82 |

|Arsenic |As |33 |75 |33 |42 |33 |

|Nickel |Ni |28 |59 |28 |31 |28 |

|Silver |Ag |47 |108 |47 |61 |47 |

|Tin |Sn |50 |119 |50 |69 |50 |

|Iodine-131 |131I |53 |131 |53 |78 |53 |

|Uranium-236 |U-236 |92 |236 |92 |144 |92 |

|Barium-141 |141Ba |56 |141 |56 |85 |56 |

AVERAGE ATOMIC MASS

Weighted Average – includes measured and %

1. Two isotopes are known for Element X. 60.0% of all the atoms of element X weight 13.2amu. The other 40.0% of the atoms weigh 14.1amu. Find the average atomic mass of Element X.

13.2 (60) + 14.1 (40) = 1356 / 100 = 13.56amu

2. Two isotopes are known for Element Y. 35.0% of all the atoms of Element Y have an atomic mass of

7. amu. 65.0% of the isotopes have an atomic mass of 32.0amu. Find the average atomic mass of Element Y.

29.7 (35) + 32.0 (65) = 3119.5 / 100 = 31.195amu

3. Element Z has three isotopes. The atomic mass and abundance of each is given below. Find the average atomic mass for element Z.

Isotope 1 112.5Z 37.21%

Isotope 2 116.9Z 44.22%

Isotope 3 114.3Z 18.57%

112.5 (37.21) + 116.9 (44.22) + 114.3 (18.57) = 11478 / 100 = 114.78amu

4. Magnesium has 3 isotopes. Find the Average atomic mass for magnesium.

Relative abundance

23Mg (Mg-23)……….23.020amu 0.500 %

24Mg (Mg-24)………..24.012amu 79.5 %

25Mg (Mg-25)………..24.997amu 20.0 %

23(0.500) + 24(79.5) + 25(20.0) = 2408.115/100 = 24.08amu

PRACTICE: ISOTOPES AND AVERAGE ATOMIC MASS

Determine the average atomic mass of the following isotopes:

1. 80% 127I, 17% 126I, 3% 128I

127 (80) + 126 (17) + 128 (3) = 12686 = 126.86 amu

100

2. 50% 197Au, 50% 198Au

197(50) + 198 (50) = 19750 = 197.5 amu

100

3. 15% 55Fe, 85% 56Fe

55(15) +56(85) = 5585= 55.85 amu

100

4. 99% 1H, 0.8% 2H, 0.2% 3H

1(99) + 2(0.8) + 3(0.2) = 101.2 = 1.012 amu

100

5. 95% 14N, 3% 15N, 2% 16N

14(95) + 15(3) + 16(2) = 1407 = 14.07 amu

100

6. 98% 12C, 2% 14C

12(98) + 14(2) = 1204 = 12.04 amu

100

Class Warm-up

1. Find the element with an atomic number of 19.___K______

2. How many protons does that element have?____19_____

3. How many electrons does that element have?___19______

4. Determine the # of protons and the # of electrons in one atom of calcium (Ca).______20_____________________

5. List the number of protons, neutrons, and electrons in the following atoms:

14 37 18

C Cl O

6 17 8

p+ __6____ ___17____ ___8___

n __8____ ___20____ __10____

e- __6____ ___17____ __8____

6. Fill in the number of protons, neutrons, and electrons in the following ions:

27 3+ 32 2-

Al S

13 16

p+ __13____ ___16____

n0 __14____ ___16____

e- __10____ ___18____

Question: Which of the following are isotopes?___d_______

4 2

a. He H

2 1

16 16

b. O O

8 7

35 35 -1

c. Cl Cl

17 17

12 14

d. C C

6 6

Question: Which are ions?____c_________

Question: Which can’t be right?_____b____________

Nuclear Chemistry

1. Types of Nuclear Reactions:

a. fission

splitting of nuclei (nucleus loses “pieces”) ex: nuclear

power, nuclear medicine, irradiation of food

b. fusion (sun)

joining of nuclei – produces uncontrollable amounts of energy

2. Types of Nuclear Emissions

Alpha Particle: 42α or 42He heaviest, least penetrating

Beta Particle: 0-1e or 0-1β middle

Gamma radiation: γ energy – not a particle very penetrating – most dangerous

3. Balancing Nuclear Equations

U-238 alpha decay 23892U ( 42He + 23490Th

Sodium -24 beta decay (emission) 2411Na ( 0-1β + 2412Mg

Try: Ra-226 alpha decay 22688Ra ( 42He + 22286Rn

Am-243 beta decay with gamma radiation also given off 24395Am ( 0 -1β + 24396Cm + γ

Rn-222 alpha decay, followed by beta emission, followed by alpha decay with gamma

Radiation

22286Rn ( 42He + 21884Po ( 0-1β + 21885At ( 42He + 21483Bi + γ

Complete: 4319K ( 4320Ca + ___0-1β ________

238U + 1n ( ___23993Np _______ + oe

Examples of Uses of Radioactive Isotopes:

1. Smoke detectors contain Am-241

2. Help us understand chemical and biological processes in plants: phosphorus-32

[pic]

Ex) in fertilizers for grass/plants

3. Food Irradiation – uses cobalt-60

[pic]

The cobalt-60 kills bacteria used in South America (where the fruits are grown) so we are not effected by the bacteria when we eat it

4. Archaeological Dating – uses carbon-14

Carbon-14 reduces in fossils as time goes on, and because we know Carbon-14’s half life, we can tell how old something is by the percentage of Carbon-14 is in it.

5. Medical Uses:

Better imagining for X-rays (technetium-99, barium-137)

Radiation treatment for cancer (iodine-131 for thyroid)

PET scan

[pic][pic]

We drink radioactive isotopes so that when we take x-rays and different scans, the different parts of our body become radioactive and can be seen. We want the radioactive isotopes that we put into our bodies to have a short half life so that it breaks down quickly and gets out of our bodies.

PRACTICE: Nuclear Decay

1. [pic] → [pic] + ______[pic]_____________

2. [pic] → [pic] + ______[pic]____________

3. [pic] → ______[pic]__________ + [pic]

4. [pic] → [pic] + __________[pic]___________

5. _____[pic]_____________ → [pic] + [pic]

6. [pic] + [pic] → _____[pic]_________ + [pic]

7. _______[pic]__________ + [pic] → [pic] + [pic]

8. [pic] + [pic] → _______[pic]___________ + (

9. [pic] + _____[pic]__________ → [pic] + [pic]

10. [pic] + [pic] → ______[pic]_________ + [pic]

11. [pic] + [pic] → _______[pic]____________

12. [pic] + [pic] → _____[pic]__________ + [pic]

13. [pic] + [pic] → [pic] + ______[pic]___________

14. [pic] + [pic] → ____[pic]_________ + [pic]

15. [pic] + [pic] → [pic] + ________[pic]____________

Half-Life –the time it takes for ½ the total amount of an isotope to undergo decay

The half life of Potassium-40 is 1.3billion years. How much of a 4.00g sample of Potassium-40 remains after 5.2billion years?

4g ( 2g ( 1g ( 0.5g ( 0.25g

1.3 billion 2.6 billion 3.9 billion 5.2 billion

years years years years

The half life of francium is 22 minutes. How much of a 2000g sample of francium remains after 66 minutes?

2000g ( 1000g ( 500 g ( 250 g

22 min 44 min 66min

Find the half-life of an isotope if 50.0g of the isotope decays to 6.25g in 3600 years.

50g ( 25g ( 12.5 ( 6.25 3600 = 1200years

1 2 3 3

A sample of francium originally has a mass of 40.0g. When the scientist returns from lunch, the mass of francium in the sample has decreased to 5.0g. If the half-life of francium is 22 minutes, how long was the scientist’s lunch break?

40 g ( 20 g ( 10 g ( 5 g

22 min 44 min 66 min lunch break was 66 minutes long

5. Graph for Half-Life

[pic]

REVIEW: What is the independent variable in this activity? What is the dependent variable? Which axis does each go on?

IV – time (x axis), DV – mass (y axis)

PRACTICE: HALF LIFE OF RADIOACTIVE ISOTOPES

1. How much of a 100.0g sample of 198Au is left after 8.10 days if its half life is 2.70 days?

100g ( 50 ( 25 ( 12.5g

2.7 days 5.4 days 8.1 days

2. A 50.0g sample of 16N decays to 12.5g in 14.4 seconds. What is its half life?

50g ( 25g ( 12.5 14.4 = 7.2 seconds

1 2 2

3. The half life of 42K is 12.4 hours. How much of a 750g sample is left after 62.0 hours?

750g ( 375g ( 187.5g ( 93.75 g ( 46.88 ( 23.4 g

12.4 hrs 24.8 hrs 37.2 hrs 49.6 hrs 62 hrs

4. What is the half life of 99Tc if a 500g sample decays to 62.4g in 639,000 years?

500g ( 250g ( 125g ( 62.5 g 639,000 years = 213,000 years

1 2 3 3

5. The half life of 232Th is 1.4 x 1010 years. If there are 25.0g of the sample left after 2.8 x 1010 years, how many grams were in the original sample?

25g ( 50 g ( 100g

1.4 x 1010 years 2.8 x 1010 years

6. There are 5.0g of 131I left after 40.35 days. How many grams were in the original sample if its half life is 8.07 days?

5g ( 10g ( 20g ( 40g ( 80g ( 160g

8.07 days 16.14 days 24.21 days 32.28 days 40.35 days

MOLAR MASS AND MOLE CONVERSIONS

Mole: 6.02 x 1023

Avogadro’s number: 6.02 x 1023 atoms = 1 mole

(Amadeo Avogadro)

Molar Mass: if you have 1 mole of an element, it weighs the atomic weight in grams

Molecular Weight

Gram Formula Mass

Conversion factors: 6.02 x 1023 atoms = 1 mole 1 mole = atomic mass (g)

Try: How many atoms are in 6.5 moles of zinc?

6.5 moles 6.02 x 1023 atoms = 3.91 x 1024 atoms

1 mole

How many moles of argon are in a sample containing 2.4 x 1024 atoms of argon?

2.4 x 1024 atoms of argon 1 mole = 3.99 mol

6.02 x 1023 atoms

**What is the mass of 2.25 x 1025 atoms of lead?

2.25 x 1025 atoms of lead 1 mole 207.2g = 7744.19g

6.02 x 1023 atoms 1 mole

How many atoms are in 10.0g of gold?

10 g gold 1 mole 6.02 x 1023 atoms = 3.1 x 1022 atoms

197.0g 1 mole

PRACTICE PROBLEMS:

a. How many moles are in:

1. 625g of copper

625g of copper 1 mol = 9.8 mol Cu

64 g Cu

2. 4.25 x 1026 atoms of barium

4.25 x 1026 atoms of barium 1 mol = 705.9 mol

6.02 x 1023 atoms

b. How many atoms are in:

1. 2.35 moles of carbon

2.35 moles 6.02 x 1023 atoms = 1.4 x 1024 atoms

1 mole

2. 4.0g of potassium

4.0 g K 1 mole 6.02 x 1023 atoms = 6.2 x 1022 atoms

39.1 g 1 mole

3. 9500g of iron

9500 g Fe 1 mole 6.02 x 1023 atoms = 1.02 x 1026 atoms

55.8g 1 mole

c. Determine the mass of:

1. 0.250 moles of aluminum

0.250 moles 27.0g = 6.75 g Al

1 mole

2. 3.48 x 1022 atoms of tin

3.48 x 1022 atoms 1 mole 118.7g = 6.86 g Sn

6.02 x 1023 atoms 1 mole

3. 4.48 x 1021 atoms of magnesium - report your answer in regular and scientific notation

4.48 x 1021 atoms 1 mole 24.3g = 0.18 g Mg or 1.8 x 10-1

6.02 x 1023 atoms 1 mole

MOLE CONVERSION HOMEWORK #1

1. Fill in the blanks below:

a. The chemical symbol for potassium is ____K_______.

b. 1.0 moles of potassium = ___6.02 x 1023_____________ atoms of potassium

c. 1.0 moles of potassium = _____39.1___________g of potassium.

d. There are ___1.38 x 1024 atoms ______ atoms in 2.3 moles of potassium.

2.3 moles 6.02 x 1023 atoms = 1.38 x 1024 atoms

1 mole

e. There are __________________ moles in 15.0g of potassium.

15.0 g K 1 mol = 0.38 mols

39.1 g K

f. There are _________________________ atoms in 10.5g of potassium.

10.5g K 1 mole 6.02 x 1023 atoms = 1.61 x 1023 atoms

39.1 g K 1 mol

2. Fill in the blanks below:

a. The chemical symbol for lead is ____Pb_______.

b. 1.0 moles of lead = ____6.02 x 1023____________ atoms of lead

c. 1.0 moles of lead = _____207.2___________g of lead.

d. There are ____1.38 x 1024 atoms _________ atoms in 2.3 moles of lead.

2.3 moles 6.02 x 1023 atoms = 1.38 x 1024 atoms

1 mole

e. There are ______0.072 _________ moles in 15.0g of lead.

15.0 g Pb 1 mol = 0.072 moles

207.2 g Pb

f. The mass of 4.2 x 1025 atoms of lead is ________14456___________________ g.

4.2 x 1025 atoms 1 mole 207.2g = 14456g

6.02 x 1023 atoms 1 mole

MOLE CONVERSION HOMEWORK #2

1. Find the mass of:

a. 0.025 moles of magnesium 24.3 g _____0.6075 g_____

1 mol

b. 1.14 moles of lithium 6.9 g _____7.866 g______

1 mol

c. 2.45 x 1023 atoms of carbon 1 mol 12.0 g _____4.88 g_______

6.02 x 1023 atoms 1 mol

2. Find the number of moles in:

a. 44g of phosphorus 1 mol ____0.025 mol_____

40.0 g

b. 2.51g of barium 1 mol _____0.02 mol_____

137.3g

c. 4.55 x 1024 atoms of zinc 1 mol ____7.6 mol_______

6.02 x 1023 atoms

3. How many atoms are in:

a. 1.55g of iron 1 mol 6.02 x 1023 atoms ___1.76 x 1023 atoms__

55.8 g 1 mol

-----------------------

1

3

4

2

Atomic number

M a s s (g)

Time (mins)

1 mole = 6.02 x 1023 atoms

1 mole = molar mass

(look it up on the PT!)

MASS (g)

PARTICLE (ATOM)

MOLE

Atomic mass

11

Na

22.9897

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