DAY 1: ATOMIC STRUCTURE & AVERAGE ATOMIC MASS

  • Doc File 1,376.00KByte



CHAPTERS 4 &25: THE ATOM AND NUCLEAR CHEMISTRY

ATOMIC STRUCTURE & AVERAGE ATOMIC MASS

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

|proton |nucleus |+1 |1 (1 amu) |1.67 x 10-24g |

|neutron |nucleus |none |1 (1 amu) |1.67 x 10-24g |

|electron |Outer energy levels |-1 |~0 (1/1840amu) |9.11 x 10-28g |

1. Complete the statements below. The statements refer to the periodic table box pictured:

a. The number “11” is the _____ATOMIC NUMBER______________. It tells the number of __PROTONS______________ and ____ELECTRONS____________ in a neutral atom of the element.

b. The number “22.9897” is the ___AVERAGE ATOMIC MASS_____________________. It tells the weighted average atomic mass of all the isotopes of an element.

c. The number “22.9897” can be rounded to 23(MASS NUMBER). This tells the total number of ___PROTONS______________ and __NEUTRONS________________ in the nucleus of the atom.

d. The number of neutrons in the nucleus of an atom can be determined by:

___MASS NUMBER – ATOMIC NUMBER = NUMBER OF NEUTRONS_____________

2. Use your periodic table to complete the chart below:

|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 |

ISOTOPES & IONS

isotope:atoms of the same element with different mass numbers

isotopicnotation: carbon -14 C-14 [pic]

|Name |Symbol |Atomic Mass Number |p |n |e |

|Beryllium-8 |Be-8 |8 |4 |4 |4 |

|Beryllium-9 |Be-9 |9 |4 |5 |4 |

ion:atoms with a charge

|Name |Symbol |Atomic Mass Number |p |n |e |

|calcium ion |Ca2+ |40 |20 |20 |18 |

|oxygen ion |O2- |16 |8 |8 |10 |

Complete the chart below:

|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.

| |Symbol |Atomic Number |Mass Number |Protons |Neutrons |Electrons |

| | | | | | | |

|Name | | | | | | |

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

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

|hydrogen ion | | | | | | |

|Carbon |[pic] |6 |12 |6 |6 |6 |

|Lithium ion |[pic]+ |3 |7 |3 |4 |2 |

|Cloride ion |[pic]- |17 |35 |17 |18 |18 |

| |[pic] |19 |40 |19 |21 |19 |

|potassium-40 | | | | | | |

| |[pic] |12 |24 |12 |12 |12 |

|magnesium | | | | | | |

|Chromium |[pic] |24 |52 |24 |28 |24 |

|Cobalt |[pic] |27 |59 |27 |32 |27 |

| |[pic]-3 |33 |72 |33 |39 |36 |

|arsenic ion | | | | | | |

|Silver |[pic] |47 |108 |47 |61 |47 |

| |[pic]+1 |47 |108 |47 |61 |46 |

|Silver Ion | | | | | | |

|Thorium-230 |[pic] |90 |230 |90 |140 |90 |

|Barium-140 |[pic] |56 |140 |56 |84 |56 |

HOMEWORK: ELEMENTS, ISOTOPES AND IONS

1. Define the following terms:

Element – simplest type of matter; contains one type of atom only

Isotope- form of an element with same number of protons, but different mass (neutrons)

Ion – a charged particle

1. Complete the chart for the elements and isotopes below:

|NAME |SYMBOL |ATOMIC NUMBER |ATOMIC MASS |PROTONS |NEUTRONS |ELECTRONS |

|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 %

USING THE WEIGHTED AVERAGE TO CALCULATE ATOMIC MASS

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 (0.60) + 14.1 (0.40) = 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 (0.35) + 32.0 (0.65) = 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 37.2%

Isotope 2 116.9Z 44.2%

Isotope 3 114.3Z 18.6%

112.5 (0.3721) + 116.9 (0.4422) + 114.3 (0.1857) = 114.78amu

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

Relative abundance

23Mg (Mg-23)……….23.0amu 0.500 %

24Mg (Mg-24)………..24.0amu 79.5 %

25Mg (Mg-25)………..25.0amu 20.0 %

23(0.0500) + 24(0.795) + 25(0.20) = 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 (0.80) + 126 (0.17) + 128 (0.03) = 126.86 amu

2. 50% 197Au, 50% 198Au

197(0.50) + 198 (0.50) = 197.5 amu

3. 15% 55Fe, 85% 56Fe

55(0.15) +56(0.85) = 55.85 amu

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

1(0.99) + 2(0.08) + 3(0.02) = 1.012 amu

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

14(0.95) + 15(0.03) + 16(0.02) = 14.07 amu

6. 98% 12C, 2% 14C

12(0.98) + 14(0.02) = 12.04 amu

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:

a. 465mL = ________________________ mL g. 0.000 000 000 440 mg = ___________________mg

b. 69,755g = _________________________ g h. 5.50 x 103 L = ____________________________L

c. 234,241 J = ________________________J i. 2.75 x 106 J = ____________________________J

d. 750,000,000,000g = _________________g j. 3.5 x 10-2 cal = ___________________________cal

e. 0.0125 cm3 = _____________________cm3 l. 2.29 x 10-6 g = ___________________________g

f. 0.000086 kPa = ____________________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?

____________________________. This can be rewritten as __________________________ or

____________________________.

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

c. 6.02 x 1023

MOLAR MASS AND MOLE CONVERSIONS

Mole: 6.02 x 1023

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

(Amadeo Avogadro)

Molar Mass: the weight in of 1 mole of an element (in grams)

CONVERSION FACTORS: 1 mole = 6.02 x 1023 atoms 1 mole = atomic mass (g)

Try:

1. 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

2. 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

3. How many moles are in 2.5g of lithium?

2.5 grams Li 1 mole = 0.36 mol

6.9 g

4. Find the mass of 4.8moles of iron.

4.8 moles 55.8 g = 267.84 g

1 mole

Two Step Problems:

1. 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

2. 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. Convert to moles:

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 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

d. Try:

How many moles is 2.50kg of lead?

Find the mass, in cg, of 3.25 x 1021 atoms of lithium

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 gPb

f. The mass of 4.2 x 1025 atoms of lead is ________14.5___________________kg.

4.2 x 1025 atoms 1 mole 207.2g 1 kg = 14.5g

6.02 x 1023 atoms 1 mole 1000 g

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 __1.42 mol_____

31.0 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. 1.55mg of iron 1g 1 mol 6.02 x 1023 atoms =1.67 x 1019 atoms

1000mg 55.8 g 1 mol

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

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

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)

HALF-LIFE PROBLEMS:

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

HOMEWORK: HALF LIFE

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

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] |

| | | |

| | | |

| | | |

| | | |

| | | |

| | | |

| |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] |

| | | |

| | | |

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

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

| |Light emissions (next chapter!) | |

| | | |

| | | |

ELEMENTS LIST TO MEMORIZE

Quiz on: ______________________________

|Element |Symbol |Element |Symbol |

| | | | |

|Hydrogen |H |Nickel |Ni |

|Lithium |Li |Copper |Cu |

|Sodium |Na |Zinc |Zn |

|Potassium |K |Manganese |Mn |

|Cesium |Cs |Iron |Fe |

|Francium |Fr |Silver |Ag |

|Beryllium |Be |Tin |Sn |

|Magnesium |Mg |Lead |Pb |

|Calcium |Ca |Aluminum |Al |

|Strontium |Sr |Gold |Au |

|Barium |Ba |Mercury |Hg |

|Fluorine |F |Plutonium |Pu |

|Chlorine |Cl |Uranium |U |

|Bromine |Br |Chromium |Cr |

|Iodine |I |Nitrogen |N |

|Helium |He | Oxygen |O |

Neon Ne Sulfur S

Argon Ar Phosphorus P

Krypton Kr Carbon C

Xenon Xe Silicon Si

Radon Rn Thorium Th

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

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

11

Na

22.9897

Calculating Your Chemistry Grade

Quiz/Tests: 55% SAMPLE STUDENT: Test Average: 81

Classwork/Labs: 35% Classwork Average: 92

Homework: 10% Homework Average: 100

MOLE

PARTICLES (ATOM)

MASS (g)

1 mole = molar mass

(look it up onthe PT!)

1 mole = 6.02 x 1023 atoms

Time (mins)

M a s s (g)

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download