Atomic Number

1
Atomic Number

• Number of Protons

Always an integer!
2
Mass Number

• Number of Protons Neutrons

Always an integer!
3
12C

• Left Superscript mass number

6
4
12C

• Left Subscript atomic number

6
5
80Br

• 35

35
Atomic Number ?
6
20Ne

• 20

10
Mass Number ?
7
27Al

• 27

13
Mass Number ?
8
40Ca

• 20

20
Atomic Number ?
9
of electrons in a neutral atom?

• Neutral atoms have the same number of electrons
  and protons.

10
Isotope

• Atoms of the same element with a different of
  neutrons

Same of protons, different of neutrons Same
atomic , different mass
11
Characteristics of Proton

• Charge 1, mass 1 amu, location inside
  nucleus

12
Characteristics of Neutron

• Charge 0, mass 1 amu, location inside
  nucleus

13
Characteristics of Electron

• Charge -1, mass 1/1836 amu or 0.0005 amu,
  location outside nucleus

14
Summary of facts for subatomic particles
Relative Mass (amu) Relative Charge Location
Proton 1.007276 or ? 1 1 Nucleus
Neutron 1.008665 or ? 1 0 Nucleus
Electron .00054858 or ? 0.0005 or ? 0 -1 Outside Nucleus
15
Ion

• An atom that has gained or lost electrons so
  carries charge

16
Positive Ion

• An atom that has LOST electrons

17
Negative Ion

• An atom that has GAINED electrons

18
Charge

• protons - electrons

19
Nucleons

• Protons Neutrons

20
atom

• Smallest bit of an element that retains the
  properties of the element.

21
atom

• Smallest bit of an element that can participate
  in a chemical reaction.

22
of neutrons

• Mass number atomic number

Subtract the atomic number FROM the mass number!
23
14C

• 8 neutrons
• 6 protons
• 6 electrons

6
of neutrons ? of protons ? of electrons
?
24
9Be

• 5 neutrons
• 4 protons
• 4 electrons

4
of neutrons ? of protons ? of electrons
?
25
40Ar

• 22 neutrons
• 18 protons
• 18 electrons

18
of neutrons ? of protons ? of electrons
?
26
15N

• 8 neutrons
• 7 protons
• 7 electrons

7
of neutrons ? of protons ? of electrons
?
27
24Mg

• Right superscript charge

2
12
28
15N

• 8 neutrons
• 7 protons
• 10 electrons (gained 3)

-3
7
of neutrons ? of protons ? of electrons
?
29
19F

• 10 neutrons
• 9 protons
• 10 electrons (gained 1)

-1
9
of neutrons ? of protons ? of electrons
?
30
16O

• 8 neutrons
• 8 protons
• 10 electrons (gained 2)

-2
8
of neutrons ? of protons ? of electrons
?
31
23Na

• 12 neutrons
• 11 protons
• 10 electrons (lost 1)

1
11
of neutrons ? of protons ? of electrons
?
32
24Mg

• 12 neutrons
• 12 protons
• 10 electrons (lost 2)

2
12
of neutrons ? of protons ? of electrons
?
33
27Al

• 14 neutrons
• 13 protons
• 10 electrons (lost 3)

3
13
of neutrons ? of protons ? of electrons
?
34
Nuclear Charge

• Charge on the nucleus only. Does not include the
  electrons.
• Always positive.
• Equals the number of protons.
• Equals the atomic number.

35
Cation

• Positive ion

36
Anion

• Negative ion

37
Daltons Model

• Billiard Ball Model

Solid Indivisible Homogeneous
38
Daltons model

1. All matter is composed of atoms.
2. Atoms of a given element are identical, atoms of
   different elements are different.
3. Atoms cannot be subdivided, created, or
   destroyed.
4. Atoms of different elements combine in small
   whole number ratios to make compounds.
5. In chemical reactions, atoms are rearranged.

39
Thomsons Model

• Plum Pudding Model

Solid Divisible Inhomogeneous contain charges!
Electrons are particles!
40

• Deflection of cathode ray

41
Thomsons model

• Thomson gets credit for discovering electron
  because he got the first numbers he found the
  charge-to-mass ratio of the electron.

42
Rutherfords Model

• Nuclear Model

Mostly empty space Divisible Inhomogeneous Contain
s a small, dense positive nucleus
43
Rutherfords model

• Nuclear Model

44
Rutherfords Experiment

• Shot alpha particles at gold foil.
• Most went through, so most of the atom is empty
  space.
• Some deflected back by small dense positive
  nucleus.

45

• Rutherfords Experiment

A very small percent of the alpha particles
deflected back Evidence for a small, dense,
positive nucleus.
Most of the alpha particles went through so most
of the atom is empty space
46
Bohrs Model

• Shell Model

47
Bohrs Model

• Shell Model

Electron is still a particle. Quantized energy
levels. Electrons move on 3-D spherical orbits.
48
Bohr Configurations

• In the NYS Reference Tables!

Bohr configurations are irregular because the
Bohr model is incorrect. You cannot predict them
for the larger atoms, even if you know the
maximum capacities of each orbit.
49
Bohr Diagram

• Sulfur 2-8-6

Valence electrons are in outermost orbit
50
Bohr Configuration

• Maximum Capacity of Orbits

Sulfur 2-8-6 3 occupied levels but only two
completely occupied levels. Read question with
care!
Orbit, n Maximum Capacity
1 2
2 8
3 18
4 32
n 2n2
51
Schrodingers Model

• Wave Mechanical Model

Electron is treated as a wave. Electron Energy is
Quantized. Most probable location orbitals.
52
Schrodingers Model

• Wave Mechanical Model

53
Lewis Dot Diagrams for Atoms

• Use dots or xs to represent the valence
  electrons.
• The symbol represents the nucleus and all the
  inner shell electrons this is the kernel of the
  atom.
• In NYS, the of dots has to match the of
  valence electrons.

54
Lewis Dot Diagrams
55
atomic mass

• The mass of the entire atom includes protons,
  neutrons, electrons.
• Expressed relative to the mass of a Carbon-12
  atom.

56
atomic mass unit

• 1 atomic mass unit ? 1/12 the mass of a C-12
  atom.
• or
• The C-12 atom has a mass of 12.000 . . . atomic
  mass units.

57
Isotopic Mass
Table of Isotopic Masses

• Mass of one specific isotope

Notice that these are decimals! Why is C-12
exactly 12.0000000?
Because C-12 is the standard!
Note we use these rarely!
58
Average atomic mass

• The weighted average of the masses of the
  naturally occurring isotopes of an element.

What are these masses in the periodic table?
Warning chemists get sloppy call this atomic
mass.
59
Average atomic mass

1. Convert abundance to decimal format.
2. Multiply abundance factor by appropriate mass.
3. Sum

60
Quick check on average atomic mass calculation.

1. Final answer must be between the highest lowest
   masses.
2. Final answer will be closest to mass of most
   abundant isotope.

61
Calculate the average atomic mass of Cl.
Convert to decimal

• 75 .75 and 25 .25
• (.75) X 35 26.25 and (.25) X 37 9.25
• 26.25 9.25 35.5 avg. atomic mass of Cl
• Ans is between 35 37, but closer to 35.

Multiply each abundance factor by appropriate mass
Add up all the terms
Quick check. Report to tenths place.
Isotope Percent Abundance
Cl-35 75
Cl-37 25
Note The NYS Regents make severe approximations
to the isotopic masses! So no worries about sig
figs!
62
Law of Conservation of Massfor ordinary chemical
and physical change

• Mass is neither created nor destroyed
• Total Mass Before Total Mass After
• Total Mass Reactants Total Mass Products

63
Law of Conservation of Massfor ordinary chemical
and physical change

• O2 2H2 ? 2H2O

Recall in this kind of problem you do NOT use
the coefficients!
32 g X g 36 g X 4 g
32 grams of oxygen reacts with X grams of
hydrogen yielding 36 g of water.
64
Chemical Equations

• Reactants ? Products
• aA bB ? cC dD
• A B are reactants.
• C D are products.

65
Law of Definite Proportions

• A chemical compound contains the same elements in
  exactly the same proportions by mass regardless
  of sample size or source.

66
Law of Definite Proportions

• NaCl is
• 39.3 Na and 60.7 Cl
• no matter how big the sample or where it is from

67
Law of Multiple Proportions

• When two or more different compounds are composed
  of the same two elements, then the ratio of the
  mass of the second element combined with a
  certain fixed mass of the first element is always
  a ratio of small whole numbers.

68
Law of Multiple Proportions

• Normalized Data!

Grams Mn Grams O
Compound A 17.16 g 5.00 g
Compound B 12.87 g 5.00 g
Compound C 11.44 g 5.00 g
Take ratios of the Mn masses!
This is the fixed mass, so you can forget about
it!
A/B 17.16/12.87 1.33 4/3 A/C 17.16/11.44
1.5 3/2 B/C 12.87/11.44 1.125 9/8
69
Relative atomic mass

• Both atomic mass units and the mole are based on
  C-12.

70
Relative atomic mass

• Dual Perspective
• Microscopic vs. Macroscopic

71
Relative atomic mass

• Take the relative atomic mass from the periodic
  table and
• Stick atomic mass unit after it to get the
  average mass of one atom or
• Stick gram after it to get the mass of one mole
  of that element.

72
Mole

• Measure of the amount of substance in terms of
  the number of particles.
• The amount of any substance that contains as many
  particles as there are atoms in 12 grams of pure
  12C.

73

• Dual Perspective

The average Li atom has a mass of 6.941 atomic
mass units. A mole of Li atoms has a mass of
6.941 grams.
74
mole

• 6.02 X 1023
• Avogadros Number

75
Molar Mass

• Mass of one mole of a substance. For elements,
  the molar mass is the relative atomic mass
  expressed in grams.

76
of moles from Table T.

• of moles Mass of sample

Molar Mass
77
1 Mole

• 6.02 X 1023

78
0.5 Mole

• 3.01 X 1023

79
0.25 Mole

• 1.50 X 1023

80
2.0 Mole

• 12.04 X 1023
• Or
• 1.204 X 1024