1. Electrons Main Concept:
The atom is composed of negatively charged electrons, which can leave the atom, and a positively charged nucleus that is made of protons and neutrons. The attraction of the electrons to the nucleus is the basis of the structure of the atom. Coulomb’s law is qualitatively useful for understanding the structure of the atom.  

2. How Particles Interact Factors affecting Coulomb’s Law
Electrons
How Particles Interact
– –
+ +
+ –
Factors affecting Coulomb’s Law 1. 2.
Ionization Energy
Photoelectron Spectroscopy (PES)
What it shows and how it shows it

3. Coulomb’s law:
- force between two charged particles is proportional to the magnitude of each of the two charges (q1 and q2)
- inversely proportional to the square of the distance, r, between them
- Potential energy is proportional to q1q2/r

4. Charges of opposite signs = the force is attractive
Charges of opposite signs = the force is repulsive

5. - First ionization energy: minimum energy needed to remove the least tightly held electron from an atom or ion
- Generally, ionization energy of any electron is the minimum energy needed to remove that electron from the atom or ion

6. - relative magnitude of ionization energy can be qualitatively estimated through Coulomb’s law
- farther electron is from nucleus = lower ionization energy
- comparing two species with the same arrangement of electrons  higher nuclear charge = higher ionization energy of an electron in a given subshell

8. Photoelectron Spectroscopy

9. Photoelectron Spectroscopy (PES) provides direct evidence for the shell model
Light
-made of photons
-energy of photon E=hv
-h is Planck’s constant
-v is the frequency of
the light
Photoelectric Effect:
- light ejects electrons from a material
- requires the photon to have sufficient energy to eject the electrons

10. - Measurement of energies provides a way to deduce the shell structure of an atom
- Intensity of the photoelectron signal for given energy is the relative number of electrons in that energy level

11. The electronic structure of atoms can be inferred from evidence provided by PES
ex: both electrons in He are identical, about
the same distance from the nucleus as in H vs
two shells of electrons in Li, outermost electron
is further from the nucleus than in H or He H Li He