DEMOCRITUS

• (470-380 BC) Proposed that matter could be cut down to its basic building blocks which he called ATOMS—indivisible particles of matter

ARISTOTLE

• (384-322 BC) All matter is made of “Earth, Air, Fire and Water” which he could prove (?) with the “green twig experiment” …. The type of matter you had was evident in the smallest amount you could see…..

• This “It is as I see it” scientific concept lasted for 2000 years.

LAVOISIER

• Law of conservation of matter- mass is neither created or destroyed during ordinary chemical reactions or physical changes

• Invented the balance• Discovered oxygen

JOHN DALTON

• (1809) He championed the ATOMIC THEORY by using atoms to explain

• Law of conservation of Matter • Law of definite proportions• Law of multiple proportions

Atomic Theory

1. All matter is composed of extremely small particles called atoms.

Atomic Theory

2. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.

Atomic Theory

3. Atoms cannot be subdivided, created, or destroyed.

Atomic Theory

4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds.

Atomic Theory

5. In chemical reactions, atoms are combined, separated, or rearranged.

BECQUEREL

• Discovered radioactivity

BEN FRANKLIN

• Discovered electricity

JJ THOMSON

• http://www.magnet.fsu.edu/education/tutorials/java/cathoderaytube/

JJ THOMSON

• Discovered the electron using a Cathode Ray Tube

• When electricity is run through an evacuated tube, a light is produced. This light is deflected by a magnet. Since it is repelled by the negative pole, the particle must be negative.

JJ THOMSON

• He reasoned that if negative particles exist, there must be positive ones.

• The electron is “swimming” in a sea of positive particles….evenly distributed --- +-+-+-

• He described the “Plum Pudding Model” of the atom.

• We aren’t familiar with Plum Pudding, so we will use a watermelon.

JJ THOMSON

JJ THOMSON

MILLIKAN

• The Oil Drop Experiment—discovered the mass and charge on an electron.

ERNEST RUTHERFORD

• Thomson’s student whose task it was to find the positive particle.

• The “Gold Foil Experiment” : alpha particles from a radioactive element was shot at a piece of gold foil. Geiger and Marsden made a counter of where the deflected particles would be.

ERNEST RUTHERFORD

• http://micro.magnet.fsu.edu/electromag/java/rutherford/

ERNEST RUTHERFORD

• Expectations: evenly distributed deflections when positive (+) hits positive (+)

• Results: Most of the alpha (+) particles went straight through! Only a very small number were deflected!

• Conclusion: Most of the atom is empty space with a dense, positive nucleus. These + particles were named protons.

BOHR

• His task was to explain these crazy results• He proposed the “Solar System” model of the atom.

• Electrons, like planets, circle the nucleus, like the

Sun.• They must be constantly moving, like planets.• It only works for hydrogen.

CHADWICK

• Thomson discovered the electron (-)• Rutherford the proton (+)• Chadwick discovered the neutral particle, the

neutron.• The neutron has a mass similar to the proton,

it is neutral, and it resides in the nucleus.

MODERN ATOMIC THEORY

• Dalton’s “indivisible atom” is not part of today’s atomic theory because…….

• Dalton’s premise that all atoms are EXACTLY the same is not part of today’s atomic theory because…….

• YOU NEED TO KNOW WHY…….

EINSTEIN & PLANCK

• Einstein discovered the photoelectric effect- when elements are heated, they always give off the same color of light.

• Planck’s work related light color and energy. • Together they reasoned that little packets of

energy (quanta) were responsible for these color changes.

Louis de Broglie

• Proposed the Wave-Particle Duality theory…….(what does that mean?)

• Remember Planck and Einstein found that when elements are heated, they give off colors of light in little packets, quanta, of photons. (cont…..)

• Well, light was thought to only be a wave…but it can do stuff. It can open your key lock, open the door at WalMart, do surgery on your eye!!

• The electron was thought to only be a particle (plum!) that can be plucked from one atom to another. But it can give off colored lights..

HENCE>>>>>>>>>>• The Wave Particle Duality Theory means:

• Light is a wave that can act like a particle

• Electrons are particles that can act like a wave

Confused yet? It gets better……

Erwin Schrodinger

• If an electron can act like a wave, I can treat its mathematics like a wave (water wave, sine wave, earthquake wave….)

• He developed mathematical equations to describe where the electrons could reside as it acts like a wave.

Schrodinger’s equations

• Are too complex for us to even look at, but……

• This is one of the first times that the mathematical equation came BEFORE the experimental data to support it.

• With the equations in hand, we knew how to look.

Werner Heisenberg• Schrodinger’s equations tell the area in which an

electron can roam as a wave.• But to see the “little guy”, you need light! This zaps

the electron with a photon so it moves! So he isn’t where you looked!!!

• Heisenberg’s Uncertainty Principle states you can NEVER know where the electron is AND how fast it is moving. One property, but not both….

QUANTUM THEORY

• So what is it? • The idea that the electrons emit/absorb light

in little packets (quanta) of energy.• But it takes on bizarre characteristics being a

particle that acts like a wave.• For us, we just need to know a general idea of

where the electrons are…..

Energy Levels

• According to quantum theory, the electrons move in regions at specific distances from the nucleus.

• We will call them energy levels.• The largest atom has 7 energy levels.• These levels have separate spaces which are

called orbitals.

The Electron Hotel!

• Imagine an atom is like a hotel….• Then the energy levels are like floors of the

hotel…..• The orbitals are like rooms on a floor.

• Because some are nicer rooms than others, they cost more (not $, but energy)

ELECTRON RULES:

1. Aufbau Principle: Enter the

atom from the lowest energy level and go up

2. Pauli Exclusion PrincipleOnly 2 electrons may enter an orbital

and they must have opposite spin.

3. Hund’s Rule:Electrons can enter orbitals with the same

energy one at a time with the same spin before they can double in with the opposite spin.

• Hopefully we all have safely returned……………..

• We are ready to USE those last three rules.

• Have your periodic table ready!!!

Electron Orbits

• The work of Bohr and the Quantum theorists have given us a picture of the electrons whizzing around the nucleus.

• The electron cloud exists as levels; these levels are shown on the periodic table (7 rows)

• Within each level (row), different shapes (spdf) due to differences in energy.

Periodic Table: Periods/GroupsPeriods=Row or Energy level

Periodic Table: Sections indicate type of orbital-s,p,d,f

Electron Energy Orbitals: H

• 4p __ __ __• 3d __ __ __ __ __• 4s __• 3p __ __ __• 3s __• 2p __ __ __• 2s __• 1s __

Orbital notation for N

• 4p __ __ __• 3d __ __ __ __ __• 4s __• 3p __ __ __• 3s __• 2p __ __ __• 2s __• 1s __

Orbital notation for K

• 4p __ __ __• 3d __ __ __ __ __• 4s __• 3p __ __ __• 3s __• 2p __ __ __• 2s __• 1s __

Orbital notation for Co

• 4p __ __ __• 3d __ __ __ __ __• 4s __• 3p __ __ __• 3s __• 2p __ __ __• 2s __• 1s __

Electron configuration for B

1s2 2s2 2p1

Electron configuration for Ni

Electron configuration for Sg

Noble gas Configuration

• Only show the configuration of the element’s row

• Put the noble gas from the previous row in [ ] followed by the complete row’s configuration.

• [He] 2s22p4 represents what element?• [Ar] 4s1 represents what element?

Noble gas configuration for Sb

Since Sb is on Row 5, that is the only row we do. To show we have finished row 4, write [Kr] and then the configuration for row 5.

Noble gas configuration for Ir

Review: Orbital notation Mn

• 4p __ __ __• 3d __ __ __ __ __• 4s __• 3p __ __ __• 3s __• 2p __ __ __• 2s __• 1s __

Review Electron configuration

Cu

Review: Noble gas configuration

Au

Review of The ATOM

• The atom is made of 3 major particles; many others found in nuclear reactors.– Proton is +, located in the nucleus, and is assigned

a mass unit of 1.– Electron is -, located in the electron cloud

surrounding the nucleus, and is assigned a mass unit of 0 (mass is ~1/2000 th the proton)

– Neutron is 0 charge (neutral), located in the nucleus, and is assigned a mass unit of 1.

Atoms

• Neutral particles• The number of protons (+) = the number of

electrons (-)

Isotopes

• Isotopes are particles that have a different number of neutrons, therefore, a different mass.

• The atomic mass on the periodic table is a weighted average of the isotopes of that element.

• Some isotopes are radioactive.

Ions

• Ions are charged particles ( + or -) based on different numbers of electrons.

• Cations are + ions resulting from a loss of electrons.

• Anions are – ions resulting from a gain of electrons.

The Periodic Table• A map of the building block of matter.

1IA

18VIIIA

11H

1.00797

2IIA Periodic Table 13

IIIA14

IVA15VA

16VIA

17VIIA

2He

4.0026

23

Li6.939

4Be

9.0122

5B

10.811

6C

12.0112

7N

14.0067

8O

15.9994

9F

18.9984

10Ne

20.179

311

Na22.9898

12Mg24.305

3IIIB

4IVB

5VB

6VIB

7VIIB

8 9VIIIB

10 11IB

12IIB

13Al

26.9815

14Si

28.086

15P

30.9738

16S

32.064

17Cl

35.453

18Ar

39.948

419K

39.102

20Ca40.08

21Sc

44.956

22Ti

47.90

23V

50.942

24Cr

51.996

25Mn

54.9380

26Fe

55.847

27Co

58.9332

28Ni58.71

29Cu63.54

30Zn65.37

31Ga65.37

32Ge72.59

33As

74.9216

34Se78.96

35Br

79.909

36Kr83.80

537

Rb85.47

38Sr87.62

39Y

88.905

40Zr91.22

41Nb

92.906

42Mo95.94

43Tc[99]

44Ru

101.07

45Rh

102.905

46Pd106.4

47Ag

107.870

48Cd

112.40

49In

114.82

50Sn

118.69

51Sb

121.75

52Te

127.60

53I

126.904

54Xe

131.30

655Cs

132.905

56Ba

137.34

57La

138.91

72Hf

178.49

73Ta

180.948

74W

183.85

75Re186.2

76Os190.2

77Ir

192.2

78Pt

195.09

79Au

196.967

80Hg200.59

81Tl

204.37

82Pb

207.19

83Bi

208.980

84Po[210]

85At[210]

86Rn[222]

787Fr[223]

88Ra[226]

89Ac[227]

104Ku[260]

105 106 107 108 109http://www.chemsoc.org/viselements/pages/periodic_table.html

What does the periodic table tell you?

4

Be

9.012

Mass Number

• The Atomic Mass shown on the periodic chart is the weighted average of the mass of all the nuclides of the element (we will get to that later) and is usually a decimal number.

• The mass number is a whole number. To count PEN, we will round the atomic mass to the nearest whole number.

Counting PEN

• Protons are equal to the atomic number. They are the ID particles of the atoms.

• How many protons does Be have?

4

Be

9.0122

Counting PEN

• Protons are equal to the atomic number. They are the ID particles of the atoms.

• How many protons does Be have?

4

Be

9.0122

Counting PEN• Neutrons have a mass

nearly equal to the proton. The mass # = the sum of P + N; therefore, N = mass# - #P (At.#)

• What is the mass # for Be?

• How many neutrons does Be have?

4

Be

9.0122

Count PEN for Ru

• Atomic Number?• Atomic Mass?• Mass Number?• P• E• N

Counting PEN for isotopes

• Isotope notationC-14 or 14

6 C

The 14 represents the mass of the nuclide (the particular atom with a mass of 14). The C represented on the periodic table has an average mass of 12.01.

The mass number for C-14 is 14, not 12

C-14

• Atomic number?• Atomic mass?• Mass number?• P• E• N

3013Al

• Atomic number?• Atomic mass?• Mass number?• P• E• N

Cf-249

• Atomic number?• Atomic mass?• Mass number?• P• E• N

Ion: Al+3

• The Al ion has a +3 charge. Does it have more or less electrons than the atom?

• Atomic number?• Atomic mass?• Mass number?• P• E• N

Ion: P5- or P-5

• The P ion has a negative 5 charge. Does it have more or less electrons?

• Atomic number?• Atomic mass?• Mass number?• P• E• N

ReviewCount PEN

At.# At. Mass

Mass #

P+ E- N

Pu

Pu-239

Pu+2

Average Atomic Mass

• The atomic mass on the periodic table is the weighted average of all isotope nuclides.

• All elements on Earth appear to have the same mix of these isotopes.

Calculate the atomic mass of B (4 decimal places)

• The natural abundance of B exists as 19.78% B-10 and 80.22% B-11.

Calculate the atomic mass of Sr (4 decimal places)

• The natural abundance of Sr exists as– 0.56% Sr-84– 9.86% Sr-86– 7.02% Sr-87– 82.56% Sr-88