Part 1 Atomic Theory

Chemistry Warm-up: Why do you think we have to learn about Chemistry in a Biology class?

A Brief History: Democritus (Fourth Century BC) –First named the “atom” –Lacked evidence John Dalton ( ) –Performed experiments to discover: Dalton’s Atomic Theory

1.All elements composed of tiny indivisible particles called atoms. 2.Atoms of the same element are identical It sure is nice hanging out with you, Carbon. Tell me about it, Carbon! 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!

Atoms of Element A Atoms of Element B What happens when they mix?

Still more of Dalton’s Atomic Theory… 3.Atoms of different elements can physically mix together or can chemically combine to form compounds. 4.Chemical reactions occur when: –atoms are separated, joined or rearranged; –however, they are never changed into atoms of another element.

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!

The three kinds of subatomic particles 1.Electrons (e - ) –Discovered by J.J. Thomson in –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

2.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 3.Neutrons (n 0 ) –Discovered by James Chadwick in –Actual mass = 1.67 x grams –No charge The three kinds of subatomic particles 1,840 times as big

In 1911, Rutherford performed an experiment: So how are all these parts put together? Thin sheet of gold foil Source of alpha particles What did this prove?

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.

The Bohr Model In 1915, Neils Bohr modified Rutherford’s “planetary” model of the atom and added the new discovery of Quantum Theory: High energy orbital Low energy orbital

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.

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

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

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

Do page 30 now

B P = _____ N = _____ E = _____ The Atomic Number Element’s Name Boron Atomic Mass B Bohr Diagram Lewis Structure

Part 2 Bonding with activities

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 MgBr 2 Bond!

Bonding and Chemical Reactions Chemical Bonding: Combining Atoms of Elements to form Chemical Compounds Hi there! I’m Nitrogen. Am I an atom or a compound? Greetings, Nitrogen. We are Hydrogen atoms. Perhaps we will change the way you think about yourself. You were right! I am now Ammonia! But, am I an atom or a compound now? Oh, you can’t be serious!

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

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

Covalent Bonds A covalent bond is a chemical bond formed by sharing electrons. Can you guess which element I am? What will complete my valence shell?

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? HH = H – H CO O O=C=O Lone pairs: Electron pairs not shared between atoms NH H H

Practice Exercises How many Bonds and Lone Pairs? 1.Write Lewis structure for F 2. 2.Write Lewis structure for O 2. 3.Write Lewis structure for N 2. 4.Write Lewis structure for ammonia, NH 3. 5.Write Lewis structure for CO 2.

Time for more Practice Page Making Ionic Bond

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)

Time to Practice Page 36 Balancing Act

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!

Organic Chemistry – VideoVideo Write the following questions in your notes (Leave space to write your answers): 1.What is organic matter? 2.Why is Carbon the “element of life?” 3.What is the Octet Rule? 4.List three Chemical Processes of Life. 5.Why is Photosynthesis considered to be the most fundamental of all life processes?

Bonding Basics Practice Answers (page 33) Ionic Bonds 1.Mg + Br 2.Pb + S 3.Al + Cl MgBr MgBr 2 PbS 2 PbSS 4+2- AlCl 3+1- AlCl 3 1-

Bonding Basics Practice Answers (page 33) Covalent Bonds 1.H + Cl 2.C + Cl 3.Si + O HClH – ClHCl CCl 4 CCl C SiO O O = Si = O SiO 2