3.03 Atomic Structure Nomenclature and Parts of the atom

Dr. Fred Omega Garces Chemistry 100

Miramar College

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3.03 Atomic Structure

January 10

Modern view of the atom What are the parts of the atom and how are these parts (especially the electrons) arranged in each atom? What makes each atom (element) different from each other ? What makes certain atoms (elements) similar to each other ?

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3.03 Atomic Structure

January 10

Planetary Model 4

5

6

78

∞

3 2

1

Nucleus

Niels Bohr (1913) Proposed the first reasonable model of the atom (hydrogen) Model of the Hydrogen atom is liken to the solar system The center is the sun (most heaviest planetary body) Planets are confined to their orbitals Planet orbits the sun The center is the nucleus (most dense) Electrons are located in discrete quantized orbitals. electron orbits the nucleus 3

3.03 Atomic Structure

January 10

Atomic Model Theories From the time of Dalton g Thomson g Rutherford g Bohr g Schrodinger, our model of the atom has undergone many modifications. The model is not finish however.

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3.03 Atomic Structure

January 10

Mass and Volume; Size

Nucleus are so dense that the size of the pea has a mass of 250 million tons. Protons in nucleus held together by nuclear binding force.

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3.03 Atomic Structure

January 10

Parts of the atom Relative mass and charge for the subatomic particles of an atom Particle

Mass

*Rel Mass

Rel Charge

(amu) e -;

electron

9.109•10 -31 Kg

1/1837

- 1.602•10 -19 C

p+;

proton

1.673•10 -27 Kg

1

+ 1.602•10 -19 C

1.675•10 -27 Kg

1

0

n;

neutron

* Relative mass: 1 amu ~ mass of proton

1amu equals exactly one-twelfth the mass of a carbon-12 isotope

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3.03 Atomic Structure

January 10

The density of the nucleus; The density of the lead-208 nucleus is 1.8•1014 g/cc. This is an extremely high density. To put it in perspective, if a paper clip had this much density, it would weigh over 10-million (107) tons. The Statue of Liberty is about 250 tons, 10,000,000 tons is 40,000 Statues of Liberty!!!

http://www.endex.com/gf/buildings/liberty/libertyfacts.htm 8

3.03 Atomic Structure

January 10

Mass of the nucleus; The total mass of the 82 electrons in a lead-208 atom is 7.5•10-26 g, the mass of the whole atom is only 3.5•10-22 g. (electrons account for only 1/2000th) I weigh about 152 lb., my mass is to the mass of the proton as the mass of a nickel is to the mass of an electron.

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3.03 Atomic Structure

January 10

Size of the Atom; An atom has a diameter of about 3.5•10-8 cm. If you could line them up with the atoms just touching, it would take 73 million (73,000,000) atoms to make a line 1 inch long.

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3.03 Atomic Structure

January 10

Why are elements so different ? (if particles are identical) Electrons dictate chemistry, it is the electron which interact with each other. Their arrangement is different for each element which give rise to the element’s different properties.

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3.03 Atomic Structure

January 10

Nomenclature:

A

X Z

chg

•  X - Symbol of element •  A - Atomic mass = no. proton + no. neutron •  Z - Atomic number = no. proton, detm' identity. •  chg - charge of atom = sum of no. p (+) & no. e (-) ( Elements with the same atomic number (Z) but different atomic mass (A) are called isotopes)

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3.03 Atomic Structure

January 10

The atoms: Example

# p

12C

6

# e- # n 6

6

Different Elements

.

Diagram

.. .. . . .. .. 7p , 7n .. .. .. .. 8p ,8n ..

e- configuration 1s2 2s2 2p2 [He]

+

6p ,6n

14N

7

7

7

2s

1s2 2s2

8

8

8

+

2p3

[He]

+

16O

2p

2s

1s2 2s2

2p

2p4

[He] 2s

2p

The periodic table give an atomic mass that is not a whole number? i.e., C = 12.011 amu, H = 1.008 amu, O = 15.9994 amu

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3.03 Atomic Structure

January 10

The atoms: Example 12

C

#p 6

# e6

#n 6

.

Isotopes

Diagram

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

e- configuration 1s2 2s 2 [He]

+

2s

6p ,6n

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C

6

6

7

1s2 2s 2

C

6

6

8

2p

2p 2

[He] +

2s

6p , 7n

14

2p 2

1s 2 2s 2

2p

2p 2

[He] +

6p , 8n

2s

2p

Isotopes - atoms with different # of neutrons and protons i.e., C-12, C-13 C-14 75% of all elements have more than one isotope. Titanium and nickel has five isotope, while fluorine and potassium have just one.

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3.03 Atomic Structure

January 10

The atoms: Example 14

14

C

C +2

#p 6

6

# e6

4

#n 8

8

Charge atoms (ions). Diagram

e- configuration

.

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

1s

2

+

6p , 8n

1s 2

6

8

8

2p2

2s

2p

2s 2

2p 0

2s

2p

2s 2

2p 4

2s

2p

[He]

+

C -2

2

[He]

6p , 8n

14

2s

1s 2 [He] +

6p , 8n

ions - charge of atom / isotope or group of atoms (+) cation (cat)

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(-) anion (ant)

3.03 Atomic Structure

January 10

The atoms:

Identifying the element (2). What is the specie with the following subatomic particles? Example ?

X 8

?

#p 8

# e?

#n

Diagram

.

..

? 17

Example 17

X 8

?

#p 8

# e6

Oxygen O

-2

.

..

9 O -2

1s 2

2s 2

2p 2

2s

2p

[He]

+

8p , 9n

Diagram

17

29

..

.

O -2

#n

e- configuration

e- configuration

..

.

3.03 Atomic Structure

Oxygen O +

-2

8p , 9n

1s

2

2s

2

2p

2

[He] 2s

2p

January 10

Atomic Nomenclature: Exercise

Protons Protons

#2 #2

#3 #3

#4 #4

30

85

33 34

Neutrons Neutrons

3535

125

45 44

81

Electrons Electrons

2828

86

36 36

54

A A (atomic (atomic Mass) Mass)

65

210 113

79

135

34

54

Charge

+2

-1

-2

0

Z No.) Z (atomic (atomic Mass)

Charge Symbol Symbol

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#1#1

30

30

+2

65Zn+2

8548

85

+2

210At-

3.03 Atomic Structure

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79Se-2

54

135Xe 222 Rn

January 10

Atomic Mass: a closer look According to the periodic table the atomic mass of carbon is 12.011 amu. Yet we just said that the mass of an atom is arrived by the number of protons and neutrons for that atom. How is it that we have 0.11 amu worth of atom. Is there such a thing as a fraction of an atom? 31

3.03 Atomic Structure

January 10

Weighted Average The mass of the elements from the periodic table is actually the weighted average. Consider the following: 8 - 7 - 6 - 6 : What is the average 8 + 7 + 6 + 6 = 27: 27 / 4 = 6.75 or 8 (.25) + 7(.25) + 6(.25) + 6(.25) = 2

+ 1.75

+ 1.5

+ 1.5

= 6.75

Now what is the atomic mass for chlorine which exist in the following abundance: Cl-35 (75.53 % ) & Cl-37( 24.47 %) At. Wt = 35(.7553) + 37(.2447) = 26.44 + 9.05 = 35.49 g/mol 32

3.03 Atomic Structure

January 10

Summary Piecing together the Atomic Structure

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3.03 Atomic Structure

January 10