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

2. A Brief History: Democritus (Fourth Century BC)
Ahem… Er, Mr. Democritus, I don’t believe this is a laughing matter.
Democritus (Fourth Century BC)
First named the “atom”
From Greek word “atomos” meaning unable to cut
An atom is the basic unit of matter
Lacked evidence
John Dalton ( )
Performed experiments to discover:
Dalton’s Atomic Theory
Would you kindly remove yourself? You’re blocking my information.

3. Dalton’s Atomic Theory
Um, who is this? He looks pretty different from you and me, Carbon.
I’m Oxygen. I am different from you, but I’m sure we could find some way to bond!
It sure is nice hanging out with you, Carbon.
All elements composed of tiny indivisible particles called atoms.
Atoms of the same element are identical
Tell me about it, Carbon!

4. Still more of Dalton’s 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.

5. Reflecting on Dalton’s Theory
Most of Dalton’s theory is still accepted. Which part do you think has been rejected?
The Atom is Divisible!
Return to Theory #1 and cross out the word “indivisible”

6. The three kinds of subatomic particles
1. Protons (p+)
Discovered in 1886, Eugen Goldstein saw cathode rays traveling against the flow.
What do you think the proton’s mass is in relation to the electron? ________________
Actual mass = 1.67 x grams
One unit of positive charge
2. Neutrons (n0)
Discovered by James Chadwick in 1932.
No charge
1,840 times as big

7. The three kinds of subatomic particles
3. 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 __________
grams

8. 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

9. 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.

10. Atomic Structure Protons and Neutrons make up the nucleus
Electrons spin around in orbitals surrounding the nucleus

11. The Bohr Model
In 1915, Neils Bohr modified Rutherford’s “planetary” model of the atom
He added the new discovery of orbitals
Outer orbitals = Max out at 8
Innermost Orbital = Maxes out at 2

12. 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.

13. Why protons? Why not neutrons? Or electrons?
Oxygen’s 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

14. Atomic Mass (AMU)
The total number of protons and neutrons is called the atomic mass.
Based on this nucleus, what is the atomic mass?
What element is it? 4 +
Helium +

15. What about those special cases?
Sometimes there are more or less neutrons in a nucleus, these are called isotopes.

16. B B The Atomic Number 5 5 Element’s Name 6 Boron 5 Atomic Mass 10.81
P = _____ 5
Element’s Name
N = _____ 6
Boron
E = _____ 5
Atomic Mass
10.81
Bohr Diagram
Lewis Structure B

17. Welcome! Please pick up your folder and go to your Science group!
Clean out your folder, leaving only your “Periodic Table Basics” worksheet in there.

18. Bonding and Chemical Reactions
Hi there!
I’m 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.
Bonding and Chemical Reactions
Chemical Bonding:
Combining Atoms of Elements to form Chemical Compounds
Oh, you can’t be serious!

19. Bonding
To achieve stability, an atom will either gain, lose or share electrons.
Ionic Bonds:
A bond that involves a transfer of electrons

20. Ionic Bonds Sodium Chlorine Sodium Chloride = Salt! Chloride Ion (+1)

21. 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.

22. 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
O=C=O C O O
Lone pairs: Electron pairs not shared between atoms H N H H

23. Bonding Basics Practice1- 2+ 1-
Ionic Bonds
Mg + Br
Pb + S
Al + Cl Br Mg Br
MgBr2 2- 4+ 2- S Pb S
PbS2 1- Cl Cl Al Cl
AlCl3 1- 3+ 1-

24. Bonding Basics Practice
Covalent Bonds
H + Cl
C + Cl
Si + O H Cl
H – Cl
HCl Cl Cl Cl C Cl Cl C Cl
CCl4 Cl Cl O Si O
O = Si = O
SiO2

25. Bond with your classmate!
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!