Ch 4 – Atomic Structure

History:1. Democritus- (400 BC) What’s the smallest possible particle? Break a rock into pieces…

eventually get to smallest possible pieces → call those “atomis” (invisible)

2. Aristotle- Everything is made of a substance called “hyle.” Re-arrange hyle to make different substances. Aristotle's philosophies accepted by Roman Catholic church - Western science in dark ages until ~ 1500’s.

3. Dalton- (1800’s) father of atomic theory 1. All elements composed of tiny, invisible particles →atoms2. All atoms of same element are identical atoms of different elements are different 3. Atoms of diff. elements combine in whole # ratios.4. Chem. occur when atoms separate from each other, join with others, but the atoms

themselves never change.

4. JJ Thompson (~1900) uses cathode ray tube & discovers the electron

5. Millikan (~1900) his oil drop experiment discovered mass/charge of electron

6. Rutherford- (1905)- Gold Foil Experiment – discovered the nucleus →(+) charged core of the atom

7. Neils Bohr- (~1910’s)- Planetary model of the atom

8. Chadwick- (1932)- discovered neutron

Subatomic particlesParticle Symbol Charge Mass in

gramsMass in amu

Proton p+ +1 1.67x10-24 1

Electron e- -1 9.11x10-28 1/1840

Neutron no 0 1.67x10-24 1

500,000,000,000,000,000,000,000,000,000,000 electrons equals 1pound2,500,000,000,000 protons side by side = 1 inch

Ch. 4 HW #1 1-5

1. Explain how Democritus came up with his theory every made of atoms:

2. Which statement would Dalton Agree with:a) Atoms are the smallest particles of matter.b) Mass of an iron atom is different from mass of a copper atom.c) Every atom of silver is Identical to every other atom of silver.d) A compound is composed of atoms of two or more different elements.

3. Since all atoms have negatively charged electrons shouldn’t every sample of matter have a negative charge? Explain.

4. Now did the results of Rutherford's Gold Foil Experiment differ from his expectations?

5. What is the charge of every nucleus (+ or -)?

Ch 4 HW #2

6. (in class)7. (in class)

8. An atom is identified as platinum- 195.a) What is the number 195 called?

b) What is the symbol with #’s?

9. Determine the number of neutrons:

a) Carbon - 13

b) Nitrogen- 15

c) Radium - 226

Ch 1 – XC Clock

Suppose a metric clock used the following system:

1 day = 10 metric hours1metric hour = 10 metric minutes1 metric minute = 10 metric seconds 1 metric second = 10 metric mini-seconds

If the metric clock reads 4hrs, 5min, 6 sec, 7 mini-sec,What time is it in the real world?

6 2 4

CCarbon12.011

Ch 4- The Periodic Table

Atomic # - # of protons- the periodic table is arranged in increasing atomic #.- since all atoms are electrically neutral # protons = #of electrons

Mass # - total mass of atom mass = protons and neutron - do not count electrons → too small!

HW # 6) (copy to separate paper!)

Element Symbol Atomic # # of protons

Potassium

5

16

Y

HW # 7)

Atomic # Mass # # Protons # Neutrons #Electrons Symbol

9 10

14 15

47 22

55 25

Writing symbols:16 ← mass # (prots & nuets)

ex: 8 ← Atomic # (prots)

Neutrons = mass- atomic= 16 – 8 = 8 Neutrons

ex: 108

Ag Neutrons = 108 – 47 = 61 N 47

Sometimes written is this form :ex: Carbon – 12 Back to P.T.

↖ mass # Look at P.T. to find atomic #

Neutrons = Mass – Atomic = 12 – 6 = 6 neutrons

ex: Uranium – 238 Neutrons = 238 – 92 = 146

6 2 4

C Carbon

12.011

Average Atomic Mass

H – 1.0079 ( Over 99% of all hydrogen's are H – 1) ( A few are H – 2, or H – 3)

C – 12.011 ( Almost all are C – 12)

Cl – 35.435 - only 2 isotopes → Cl – 35 & Cl – 37 75% in nature are Cl – 3525% are Cl – 37So these are weighted averages

14) Cu had 2 isotopes: Cu – 63 , Cu – 65. Given that the ave atomic mass is 63.546 amu, which isotope is more abundant?

(finish for HW)

Calculating Ex) Element x has 2 natural isotopes. One isotope with mass 10.012 amu has a relative abundance of 80.09%. Calculate the atomic mass and the name of the element.

10X: 10.012 amu x 0.1991 = “X: 11.009 amu x 0.8009 =

Ch 4 HW # 4 10-15

Isotopes Isotopes of the SAME ELEMENT obviously have the same # of protons, differ in # of Neutrons

Ex. Write the chemical symbol and find # of Neutrons for: Carbon-12 and Carbon-13

126 C 13

6 C

HW #12) Determine # of prots, elects, Neuts for the 5 isotopes of zincp+ e- N

Zn-64 30 30 34Zn-66 30 30 36Zn-67 30 30 37Zn-68 30 30 38Zn-70 30 30 40

Atomic Mass ↓.00000000000000000000003g

1 Flourine atom-3.155x10-23 g 1 arsenic atom-1.244x10-22 gNot practical!

Decide to call the mass of 1 proton=1 atomic mass unit -since prots and Neuts are close, but slightly different, decide to take Carbon-12 (6 prots, 6 Neuts) ÷ by 12 = 1 amu

Element Symbol # Protons # Neutrons Row (period) C5olumn (Group)

Aluminum Al 13 14 3 13

Carbon C 6 6 2 14

Chlorine Cl 17 18 3 17

Chromium Cr 24 28 4 6

Cobalt Co 27 32 4 9

Copper Cu 29 35 4 11

Gold Au 79 119 0 11

Helium He 2 2 1 18

Hydrogen H 1 0 1 1

Iron Re 26 30 4 8

Krypton Kr 30 47 4 18

Lead Pb 82 125 6 14

Mercury Hg 80 121 7 12

Nitrogen N 7 7 2 15

Potassium K 19 20 4 1

Element Symbol # Protons # Neutrons Row (period) Column (Group)

Silver Ag 47 61 5 11

Sodium Nu 11 12 3 1

Sulfur S 16 16 3 16

Uranium U 92 146 7 -

Zinc Zn 30 35 4 12

1

1

HHydrogen

1.0074

Electron Shells Worksheet1.

21

3

LiLithium6.941

2.

21

3

LiLithium6.941

2.

1p0n

1 Electron

3p4n

23

_

__Boron

______

3.

_p_n

__

_

__Nitrogen______

4.

_p_n

28

2

12

MgMagnesium

24.3

5.

12p18n

__

_

__Aluminum

______

6.

_p_n

28

7

_

__Chlorine______

7.

_p_n

28

8

_

__Argon

______

8.

_p_n

30

ZnZinc65

10.

30p35n

288

1

_

KPotassium

______

9.

_p_n

Ch 4 HW #3

10) How are isotopes of the same element alike? How are they different?

11) Three isotopes of oxygen are Oxygen – 16, Oxygen – 17, and Oxygen – 18, write the chemical symbol.

12) ( in class )

13) There are 3 isotopes of silicon with mass #’s 28, 29, 30. The atomic mass of silicon is 28.086 amu. Which is most abundant?

14) The element copper has 2 naturally occurring isotopes : 6329 Cu, 65

29 Cu. The relative abundances and atomic masses are:

Calculate the average atomic mass.Cu – 63 .692 x 63 = 43.47Cu – 65 .308 x 65 = 20.02

63.49

15) List the # of protons, neutrons, electrons

a) 2713Al b) 44

20Ca c) 31H d) 18

8O e) 7834Se

p+

no

e-

Chapter 25 Nuclear Chemistry Ex: Carbon – 14

68PN

Radioisotopes – isotopes that are radioactive because they have unstable nuclei.

They undergo radioactive decay - give up energy from the nuclei ( some nuclei break apart. )

Types of Radiation Alpha radiation – a helium nucleus is emitted from a radioactive sourceEx) 238

92 U → 22490 Th + 4

2 He Uranium – 238 Thorium – 234 Alpha particle

238

92U

42 He

22490 Th

Low EnergyLow Penetrating Power

(α emission)

Beta radiation – an unstoppable nucleus decays, releases a beta particle - a neutron decomposes into a proton and an electron

10N → 1

1H + 0-1e

Neutron Proton Electron (beta particle)

Ex) 146C → 14

7N + 0-1e

Radioactive Stable Beta Carbon – 14 Nitrogen – 14 Particle

↑ ↑p=6 p=7N=8 N=7

Gamma radiation – an unstable nucleus decays, releasing high energy electromagneticradiation.

Ex) 23090Th → 226

88Ra + 42He + Y

Thorium – 230 Radon – 226 Alpha Gamma Particle Ray

Name the emitted particle and find the new nuclei created:Ex) 218

87fr → 21485At + 4

2He

24195Am → 4

2He + 23793Np

23592U → 90

38Sr + 14458Ce + 1

0N + 4 0-1e

10N + 239

94Pu → 14458Ce + 90

38Sr + 6 10N + 2 0

-1e

Ch 25 HW#1

1) What part of the atom changes during radioactive decay?

2) Tell how alpha beta and gamma radiation are distinguished based on:a) mass b) charge c) penetrating power

4 2

0 -1 β

3) The disintegration of the radioisotope radium-226 produces an isotope of the element radon and alpha radiation write eqn: 226 88 Ra → 222

88 Rn + 4 2

4 +2 Low

0 (negligible) -1 Mid

No mass No charge high

4) Write nuclear eqns:(positron)

a) 30 15 P to 30 14 Si 30 15 P → 30

14 Si + 0 1 β

b) 13 6 C to 12 6 C 13

6 C → 12 6 C + 1 0 n

5) Complete: a) 3015P → ____ + 0

-1eb) ___ →14

7N + 0-1e

c) 23892U → 234

90Th + ___d) 141

56BA → ___ + 0-1e

6) Beta decay the following:a) 90

38Sr →b) 14

6C →c) 137

55Cs → d) 239

93Np →

Half Life (t ½)-The time required for ½ the atoms of a radioisotope to decay.

Ex 1) Nitrogen – 13 emits beta radiation and decays to Carbon – 13 with a half life of 10 min. with a starting mass of 2.00gof N – 13,

a) how long is 4 half lives?b) how many grams of N – 13 still exist after 3 half lives?

Carbon Dating - developed in 1940’s - 14

6C → 147N + 0

-1e- t1/2 = 5730 years- fairly accurately dates non-living things 200-50,000 yrs

How do we date the dinos? Use a radioisotope with a longer ½ life- uranium – 238 → t1/2 = 4.5 x109 yrs ( 4,500,000,000,) ( 4.5 billion yrs )

- use this to age certain rocks, all the back to beginning ofour solar system 4.6 billion years.

Ex 2) What is the ½ life of this radioisotope ? 5 yrsIf you had 20.0 g of it, how much remains after 10 years?

2 half-lives5g

5 10 15 20 25

25-

50-

100-

amt %

t(yrs)

Nuclear Fission and FusionFission-the splitting of a nucleus into smaller fragments caused by bombarding it with neutrons

-releases enormous amounts of energy( 1 kg of U-235 = 20000 tons of TNT)

→ ↗ ↘

235 92 U 236 92 U 91 36 Kr

1 0 N + 235 92 U → 236 92 U → 91 36 Kr + ___ + 3 1 0 N

Fusion – 2 nuclei combine to produce a nucleus of heavier mass In the sun:4 1

1H + 2 0-1e → 4

2He + energy

- fusion releases more energy than fission but requires high temps → 40,000,000 0C

Cold fusion2

1H + 31H → 4

2He + 10N + energy

Ch 25 HW #27) A sample of thorium – 234 has a half-life of 25 days. Will all the thorium undergo radioactive decay in 50 days?

10g → 5g → 2.5g9) Explain nuclear chain reaction.

10) How is the chain reaction uncontrolled in a reactor?

11) Name a natural nuclear fusion reactor

12) What are advantages of producing electricity in a fusion reactor?

13) write: a) a radon emits an alpha particle to form polonium – 218 Rn → He + Pob) Radium – 230 is produced when thorium 234 emits alpha

c) When polonium – 210 emits alpha particle, product is Pb – 206 Po → Ne + Pb

Graph the decay of Thorium 234

100

80

60Remaining % 40

20

20 40 60 80 100 Days

a) What percent after 60 days?b) How many grams of a 250g sample remain

after 40 days?c) How many days would pass while 44g decayed

to 11g?d) What is half-life?

Ch 3, 4, 25 Reviews

Ch 3 – how many seconds are in 3.7 days?3.7 days 24hrs 60 min 60sec

1days 1hrs 1min = sec

-What values does 5.0g of Al occupy ( density of Al is 2.80g/Dm

3 )

Ch 6 – 30) Element # of

ProtonsMass Number

# of Electrons

Atomic # Number Neutrons

Si 15

1 2

50 24

88 38

32) List the # of Protons, Neutrons, Electrons for each a) 27

13Al b) 4420Ca c) 3

1H

43) What is the average mass of lead?204

82Pb @ 1.37%

20682Pb @ 26.26%

20782Pb @ 20.82%

20882Pb @ 51.55%

Ch 25 – 24 ) Write the symbol and state the charge for each:a) alpha particleb) beta particlec) gamma ray

34) A patient is administered 20mg of iodine – 131, How much of the isotope will remain In the body after 40 days id the half-life of I – 131 is 8 days?

1 2 3 4 520mg → 10mg → 5mg → 2.5mg → 1.25mg

↙.625mg