25 th Amendment is Ratified (1967) Reading for Thursday: Chapter 5 sections 6-11 Reading for Thursday: Chapter 5 sections 6-11 Homework 4 – Due Thursday 2/12/15 Homework 4 – Due Thursday 2/12/15 Chapter 4 #'s 2-22 (even), 28, 30, 35, 36, 38, 40, 44, 46, 52, 54, 59, 60, 66 (only assignment from chapter 4) Chapter 4 #'s 2-22 (even), 28, 30, 35, 36, 38, 40, 44, 46, 52, 54, 59, 60, 66 (only assignment from chapter 4) Homework 5 – Due Tuesday 2/17/15 Homework 5 – Due Tuesday 2/17/15 Chapter 5 #'s 18, 20, 22, 34, 36, (all), 55, 56, 61, 62, 70, 72, 94 (only assignment from chapter 5) Chapter 5 #'s 18, 20, 22, 34, 36, (all), 55, 56, 61, 62, 70, 72, 94 (only assignment from chapter 5)

Foiled again

The Atom REALLY early atomic theory… REALLY early atomic theory… Democritus ~350 BC Democritus ~350 BC Atomos - Greek meaning indivisible Atomos - Greek meaning indivisible Modern Definition: Modern Definition: Smallest piece that matter can be broken up into and still maintain the properties of an element Smallest piece that matter can be broken up into and still maintain the properties of an element

My Atom Broke Subatomic Particles Subatomic Particles Nucleus Nucleus Protons – p + Protons – p + Carry a single positive charge Carry a single positive charge Number of p + = ATOMIC NUMBER Number of p + = ATOMIC NUMBER

My Atom Broke Subatomic Particles Subatomic Particles Nucleus Nucleus Neutrons – n o Neutrons – n o No charge No charge # can vary from atom to atom # can vary from atom to atom Roughly the same size as p + Roughly the same size as p +

My Atom Broke Subatomic Particles Subatomic Particles Outside the nucleus Outside the nucleus Electrons – e - Electrons – e - negative charge negative charge 1/1900th the size of p + and n o 1/1900th the size of p + and n o Responsible for most of the chemistry that ever happens Responsible for most of the chemistry that ever happens

Atoms vs. Ions Atoms are !!!!! Atoms are NEUTRAL!!!!! This means that they have zero charge This means that they have zero charge #p + = #e - #p + = #e -

My Atom Broke Subatomic Particles Subatomic Particles Nucleus Nucleus Neutrons – n o Neutrons – n o No charge No charge # can vary from atom to atom # can vary from atom to atom

Mass of n o about equal to mass of p + Do each of these atoms have the same mass? Isotopes: Atoms having the same atomic number, but different atomic masses

Atom notation E A Z Symbol of element Atomic number Mass number= # p + + # n o S 16

32 16 A Z S E S S S S Shorthand: Sulfur-33 S S

Give the atom notation for the following: 1) an atom with 82 p + and 126 n o 2) an atom of iron with 28 n o 3) an atom of element 29 having 34 n o Pb Fe Cu 82 p n o =

24 Cr 53 Atomic Notation Atomic Number Mass Number Number of p + Number of n o Number of e Bi I

Name that Isotope Hydrogen has 3 isotopes hydrogen-1 has zero n o hydrogen-2 has 1 n o hydrogen-3 has 2 n o 1H1H1H1H 2 H or D or deuterium 3 H or T or tritium

Information from the Periodic Table = amu (atomic mass) = amu (atomic mass) (atomic number) 20 = (atomic number) 8 =

Atomic Masses Measured in the unit amu Stands for atomic mass unit Defined as 1/12 th the mass of a 12 C atom 35 Cl = amu 50 V = amu 79 Br = amu Are these what the P.T. say?

All Isotopes are NOT Created Equal Weighted averages Weighted averages “Normal averages” assume that everything counts the same. “Normal averages” assume that everything counts the same. Splitting the dinner bill assuming everyone ate and drank the same amount Splitting the dinner bill assuming everyone ate and drank the same amount Weighted averages take into account the fact that everything does NOT count the same. Weighted averages take into account the fact that everything does NOT count the same. Making my brother pay a larger part of the dinner bill because he ate more. Making my brother pay a larger part of the dinner bill because he ate more.

All Isotopes are NOT Created Equal Weighted averages Weighted averages An equation (oh crap) An equation (oh crap) 35 Cl = amu 35 Cl = amu Abundance = 75.77% Abundance = 75.77% 37 Cl = amu 37 Cl = amu Abundance = 24.23% Abundance = 24.23% These must be the only 2 isotopes... Why? These must be the only 2 isotopes... Why?

35 Cl = amu Abundance = 75.77% 37 Cl = amu Abundance = 24.23% x x = 35.45amu Where have I seen this before? Periodic Table gives AVERAGE ATOMIC MASS in amu!! = = All Isotopes are NOT Created Equal

78.90% of all magnesium is 24 Mg  amu 10.00% of all magnesium is 25 Mg  amu 11.10% of all magnesium is 26 Mg  amu 11.10% % = amu A Problem! What is the average atomic mass of magnesium?

Another Problem! Lead has 4 isotopes, the masses and abundances of which can be found in the following table. Your job? Calculate the isotope mass of lead-207. lead amu 1.40% lead amu 24.10% lead-207???? lead amu 52.40% ???? 22.10% X = Lead-207 = amu