Atomic Theory

1
Part 1

• Atomic Theory

2
Chemistry Warm-up

• Why do you think we have to learn about Chemistry
  in a Biology class?

3
A Brief History

• Democritus (Fourth Century BC)
• First named the atom
• Lacked evidence
• John Dalton (1766-1844)
• Performed experiments to discover
• Daltons Atomic Theory

4
Daltons Atomic Theory
Um, who is this? He looks pretty different from
you and me, Carbon.
Im Oxygen. I am different from you, but Im
sure we could find some way to bond!
It sure is nice hanging out with you, Carbon.

1. All elements composed of tiny indivisible
   particles called atoms.
2. Atoms of the same element are identical

Tell me about it, Carbon!
5
Atoms of Element A
Atoms of Element B
What happens when they mix?
6
Still more of Daltons Atomic Theory

• Atoms of different elements can physically mix
  together or can chemically combine to form
  compounds.
• Chemical reactions occur when
• atoms are separated, joined or rearranged
• however, they are never changed into atoms of
  another element.

7
Reflecting on Daltons Theory

• Most of Daltons theory is still accepted.
  Which part do you think has been rejected?

The Atom is Divisible!
8
The three kinds of subatomic particles

• Electrons (e-)
• Discovered by J.J. Thomson in 1897.
• He used a cathode ray tube
• In 1916, Robert Millikan discovered the mass was
  1/1840 H, and the charge was one unit of negative
  charge.
• Actual mass 9.11 x 10-28 __________

grams
9
The three kinds of subatomic particles

• Protons (p)
• Discovered in 1886, Eugen Goldstein saw cathode
  rays traveling against the flow.
• What do you think the protons mass is in
  relation to the electron? ________________
• Actual mass 1.67 x 10-24 grams
• One unit of positive charge
• Neutrons (n0)
• Discovered by James Chadwick in 1932.
• Actual mass 1.67 x 10-24 grams
• No charge

1,840 times as big
10
So how are all these parts put together?

• In 1911, Rutherford performed an experiment

What did this prove?
Source of alpha particles
Thin sheet of gold foil
11
Atoms are mostly empty space

• Rutherford proposed that the atomic structure was
  like planets around the sun
• This did not account for very specific traits
  that atoms possessed.

12
The Bohr Model

• In 1915, Neils Bohr modified Rutherfords
  planetary model of the atom and added the new
  discovery of Quantum Theory

High energy orbital
Low energy orbital
13

• What makes atoms different from each other, if
  they have the same basic parts?

The Atomic Number
Definition The number of protons in the nucleus
of an atom of that element.
14
Why protons?Why not neutrons?Or electrons?

• Oxygens Atomic Number is 8.
• How many protons does it have? _______
• How many neutrons does it have? ________
• How many electrons does it have? ________
• Wait a minute, how do we know we have that many
  of each atomic component?

8
8
8
15
Mass Number

• The total number of protons and neutrons is
  called the mass number.

Based on this nucleus, what is the mass
number? What element is it?
4

Helium

16
What about those special cases?

• Sometimes there are more or less neutrons in a
  nucleus, these are called isotopes.

17
Do page 30 now
18
The Atomic Number
B
5
5
P _____
6
N _____
Elements Name
Boron
5
E _____
Atomic Mass
10.81
Bohr Diagram
Lewis Structure
B
19
Part 2

• Bonding with activities

20
Bond with your classmate! (page 37)

• Each of you will have an element.
• The charge or oxidation number is on the
  element.
• Your goal is to bond with as many of your
  classmates as possible.
• Balance your equations!
• i.e., Magnesium (Mg) and Bromine (Br) must make
  MgBr2

Bond!
21
Bonding and Chemical Reactions
Hi there! Im Nitrogen. Am I an atom or a
compound?
You were right! I am now Ammonia! But, am I an
atom or a compound now?
Greetings, Nitrogen. We are Hydrogen atoms.
Perhaps we will change the way you think about
yourself.

• Chemical Bonding
• Combining Atoms of Elements to form Chemical
  Compounds

Oh, you cant be serious!
22
Bonding
To achieve stability, an atom will either gain,
lose or share electrons.

• Ionic Bonds
• A bond that involves a transfer of electrons

23
Ionic Bonds

• Sodium Chlorine

Chloride
Sodium Chloride Salt!
Ion (1)
Ion (-1)
24
Covalent Bonds
Can you guess which element I am?
What will complete my valence shell?

• A covalent bond is a chemical bond formed by
  sharing electrons.

25
Different types of Covalent Bonds

• Single Bond One pair of shared electrons
• Double Bond Two pairs of shared electrons
• Triple Bond Three pairs of shared electrons
• Hydrogen Cyanide (HCN) can form this.
• Can you?

H H
H
H
C
O
OCO
O
Lone pairs Electron pairs not shared
between atoms
N
H
H
H
26
Practice ExercisesHow many Bonds and Lone Pairs?

• Write Lewis structure for F2.
• Write Lewis structure for O2.
• Write Lewis structure for N2.
• Write Lewis structure for ammonia, NH3.
• Write Lewis structure for CO2.

27
Time for more Practice

• Page 34-35 Making Ionic Bond

28
Chemical Reactions

• Any process in which a chemical change takes
  place.
• Slow occurring (i.e., Iron and Oxygen ? Rust)
• Quickly occurring (i.e., Combustion Reaction)

29
Time to Practice

• Page 36 Balancing Act

30
Quiz Time!

• Put your Bonding with Classmate and Bonding
  Basics sheet in your folder.
• Put your folder in the in-box.
• Clear off your table and keep out a pen or
  pencil.
• When you are done, get out a sheet of paper and
  write down the video questions.
• Good luck!

31
Organic Chemistry Video

• Write the following questions in your notes
• (Leave space to write your answers)
• What is organic matter?
• Why is Carbon the element of life?
• What is the Octet Rule?
• List three Chemical Processes of Life.
• Why is Photosynthesis considered to be the most
  fundamental of all life processes?

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Bonding Basics Practice Answers (page 33)
1-
1-
2

• Ionic Bonds
• Mg Br
• Pb S
• Al Cl

Mg
Br
Br
MgBr2
4
2-
2-
Pb
S
S
PbS2
1-
Cl
Cl
Al
Cl
AlCl3
3
1-
1-
33
Bonding Basics Practice Answers (page 33)

• Covalent Bonds
• H Cl
• C Cl
• Si O

H
Cl
H Cl
HCl
Cl
Cl
CCl4
C
Cl
Cl
C
Cl
Cl
Cl
Cl
Si
O
O Si O
SiO2