1 volt = 1 joule / 1 coulomb

1 joule = 1 volt • 1 coulomb

1 joule 1 volt • 1 coulomb

=

x 1 volt • 1.6 x 10-19 coulomb

How much energy would it take to move an electron across a potential difference of 1 volt?

x = 1.6 x 10-19 joules AKA… an electron-volt

= 1eV

Photoelectron Spectroscopy (PES): Provides direct evidence that electrons exist at certain energy levels.

•Atom is bombarded with photons•Photons are absorbed and electrons are emitted•The electrons are collected and their energy analyzed

KE = h – work.(binding energy)

Based on the Photoelectric Effect

Einstein’s Photoelectric Effect Equation

Ephoton = work required to eject the electron + KE(ionization energy)

Discovered by Heinrich Hertz …Explained by Albert Einstein

Photoelectron Spectroscopy (PES): Provides direct evidence that electrons exist at certain energy levels.

If this is sufficiently high, electrons can be ejected from any energy level in an atom…one e- per atom per photon

Thus, for many atoms, electrons will be ejected from all possible energy levels.

(MJ/mole e-)

Axes for a PhotoElectron Spectrum

PhotoElectron Spectrum for _________

(MJ/mole e-)

▲Work needed to remove the electron from the atomi.e. “The ionization energy”

1310 kJ/mole e-13.6 eV

← the single 1s electron

The Binding Energy

(1,310,000 J /mole e-) (1 mole e-/6.02 x 1023 ) ( 1 eV/1.6 x 10-19 J) = 13.6 eV

hydrogen

(gotten by knowing the energy of the photon and the KE of the photo-electron)

PhotoElectron Spectrum for helium

(MJ/mole e-)

← the two 1s electrons

▲Work needed to remove one of the 1s electrons from the atom

Why is the binding energy for a 1s electron in helium (24.6 eV) larger than the value for the removal of the electron in hydrogen (13.6 eV) ?

MORE PROTONS IN THE NUCLEUS!

24.6 eV

PhotoElectron Spectrum for lithium

← the two 1s electrons← the single 2s electron

(MJ/mole e-)

What is the first ionization energy for lithium in eV?5.4 eV

Why is this value smaller than the first ionization energy in He (24.6 eV)? Core Shielding

PhotoElectron Spectrum for boron

← the two 1s electrons

← the two 2s electrons↓ the single 2p electron

(MJ/mole e-)

Why is the binding energy for the 2s electrons (1.36 MJ/mole e-) a bit higher than that of the 2p electron (0.80 MJ/mole e-)?

Due to the penetration of the 2s orbital relative to the 2p orbital.

PhotoElectron Spectrum for __________

(MJ/mole e-)

← the two 3s electrons← the six 3p electrons

↑ the one 3d electrons

↓ the two 4s electrons

What is the relative energy of the 4s electrons compared to the 3d electron once the atomic structure is configured?

The 4s electrons represent a higher energy.

scandium

PhotoElectron Spectrum for Scandium

(MJ/mole e-)

← the two 3s electrons← the six 3p electrons

↑ the one 3d electrons

↓ the two 4s electrons

Why do you think that the 4s electrons has a higher energy than the 3d electron?The implication is the 3d electron shields the 4s electrons once the 3d begins to fill.

PhotoElectron Spectrum for Scandium

(MJ/mole e-)

← the two 3s electrons← the six 3p electrons

↑ the one 3d electrons

↓ the two 4s electrons

Which electrons, one of the 4s electrons or the 3d electron, would be easiest to remove? What would the first ionization energy be in kJ/mole e-?

One of the 4s electrons, I.E.1= 630 kJ/mole