Presentation on theme: "Chemistry Why do you think we have to learn about Chemistry in a Biology class?"— Presentation transcript:
Chemistry 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” From Greek word “atomos” meaning unable to cut An atom is the basic unit of matter –Lacked evidence John Dalton (1766-1844) –Performed experiments to discover: Dalton’s Atomic Theory Ahem… Er, Mr. Democritus, I don’t believe this is a laughing matter. Would you kindly remove yourself? You’re blocking my information.
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!
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! Return to Theory #1 and cross out the word “indivisible”
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 10 -24 grams –One unit of positive charge 2.Neutrons (n 0 ) –Discovered by James Chadwick in 1932. –Actual mass = 1.67 x 10 -24 grams –No charge The three kinds of subatomic particles 1,840 times as big
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 10 -28 __________ grams
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.
Atomic Structure Protons and Neutrons make up the nucleus Electrons spin around in orbitals surrounding the nucleus
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
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
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
What about those special cases? Sometimes there are more or less neutrons in a nucleus, these are called isotopes.
B P = _____ N = _____ E = _____ 5 6 5 5 The Atomic Number Element’s Name Boron Atomic Mass 10.81 B Bohr Diagram Lewis Structure
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.
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.
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
Bonding Basics Practice Covalent Bonds 1.H + Cl 2.C + Cl 3.Si + O HClH – ClHCl CCl 4 CCl C SiO O O = Si = O SiO 2
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… MgBr 2 Bond!