Unresolved: The Collapsing Atom Paradox Unresolved: Chemical Periodicity

Unresolved:The Collapsing Atom Paradox

Unresolved: Chemical Periodicity

Unresolved: Heated metal atoms emit colored light

Unresolved: Electrified gases emit Line Spectra

Unresolved: Rydberg Equation

22

21

111

nnRH

n2 > n1… whole numbers

RH = 1.097 x 107 m-1

New model…..

Electrons as particles in Orbit (Bohr)

Now we have angular momentum, L, whichBohr hypothesizes

Is QUANTIZED

And we need to equate the centripetal (accelerating and electrostatic) forces

…the energy of an electron in

orbit:2

-18 J 102.18

n

• The lowest energy state of an atom is called the ground state (an electron with n = 1 for a hydrogen atom)

Absorption and emission of energy by the hydrogen atom. An electron that absorbs energy is raised to a higher energy level. A particular frequency of light is emitted when an electron falls to a lower energy level.

Bohr’s Model

• The lowest energy state of an atom is called the ground state (an electron with n = 1 for a hydrogen atom)

Absorption and emission of energy by the hydrogen atom. An electron that absorbs energy is raised to a higher energy level. A particular frequency of light is emitted when an electron falls to a lower energy level.

Bohr’s Model

…the energy of an electron in orbit: 2

-18 J 102.18

n

• The lowest energy state of an atom is called the ground state (an electron with n = 1 for a hydrogen atom)

Absorption and emission of energy by the hydrogen atom. An electron that absorbs energy is raised to a higher energy level. A particular frequency of light is emitted when an electron falls to a lower energy level.

Bohr’s Model

…the energy of an electron in orbit: 2

-18 J 102.18

n

Ephoton = hν = hc/λh = 6.63 x 10-34 J·sc = 3.00 x 108 m/s

• The lowest energy state of an atom is called the ground state (an electron with n = 1 for a hydrogen atom)

Absorption and emission of energy by the hydrogen atom. An electron that absorbs energy is raised to a higher energy level. A particular frequency of light is emitted when an electron falls to a lower energy level.

Bohr’s Model

…the energy of an electron in orbit: 2

-18 J 102.18

n

Ephoton = hν = hc/λh = 6.63 x 10-34 J·sc = 3.00 x 108 m/s

2218 11

1018.2hl

electron nnJxE

Unresolved:Multi-electron atomic spectra

New model…..

Einstein saysE = mc2

Einstein & Planck sayEphoton = hn

mv

hmc

h

mchc

hE

2

for a photon

for any object

Electrons as Orbital Standing Waves

If this were a standing sound wave what would you hear

at the nodes?

If this were a standing electron wave what would you detect at the nodes?

Orbital Shapes on the Web

0 5 10 15 20 250

0.5

1

1.5

2

2.5

3

First Ionization Energy vs Atomic Number

1st...

IE (

kJ/m

ol

x 10

-3)

0 5 10 15 20 250

2

4

6

8

10

12

14

16

Ionization Energy vs. Atomc Number

1st IE2nd IE3rd IE

IE (

kJ/m

ol

x 10

-3)

electron waves of an electron trapped in a corral of iron atoms

Electrons as Orbital Standing Waves

If this were a standing sound wave what would you hear

at the nodes?

How the orbitals overlap in an atom

0 5 10 15 20 250

0.5

1

1.5

2

2.5

3

First Ionization Energy vs Atomic Number

1st...

IE (

kJ/m

ol

x 10

-3)

0 5 10 15 20 250

2

4

6

8

10

12

14

16

Ionization Energy vs. Atomc Number

1st IE2nd IE3rd IE

IE (

kJ/m

ol

x 10

-3)

Electrons as a linear standing wave

Where L is the total length, λ is the wavelength, and n is an integer.

n

L2

The only waves that can occur are those for which a half-wavelength is repeated exactly a whole number of times (n times).

n

L2

(n = 3 in this case)

Electrons as a linear standing wave