12. Atomic Structure (HL) Flashcards
Ionization energy
Energy required to remove one electron from each atom in one mole of gaseous atoms under standard conditions
Unit for ionization energy
kJ/mol
What is Planck’s constant?
6.63 x 10^-34 Js
What is relationship between energy and frequency?
Energy = hv (Planck’s constant x frequency of light)
How do you calculate speed of light?
c= v x lambda (frequency x wavelength)
What can you derive from the two equations: E= hv and c= v*lambda
E= hc/lambda a.k.a the energy of photons
What is first ionization energy?
Energy required to remove one mole of electrons from one mole of gaseous atoms to produce one mole of gaseous 1+ ions
What is second ionization energy of magnesium?
Mg+ –> Mg2+ + e-
Why are ionization energies always positive?
They have to be added to overcome electrostatic attraction between nucleus and valence electrons hence it is endothermic
Why is 2nd ionization energy higher than the first?
As first electron is removed, effective nuclear charge increases and charge becomes positive. Increase in attraction means more energy is required to overcome
What should you remember when calculating ionization energy?
You have to multiply e=hv into 6.02*10^23 as you are calculating for 1 mole (Unit becomes kJ/mol)
What is the energy of convergence limit?
It is the energy absorbed from n=1 to n=infinity
Successive ionization energies
Consecutive energies required when removing electrons until only nucleus remains
What should you always refer to in an answer about ionization energies?
- Proton number
- Shielding effect
- No. of energy levels
- Atomic radius
- Effective nuclear charge
What is trend of ionization energy down a group?
It decreases as:
- proton number increases but
- energy levels increase
- shielding effect increase so effective nuclear charge decreases
What is trend of ionization energy across a period?
It generally increases as:
- proton number increases
- shielding effect remains the same so effective nuclear charge increases and is hence stronger requiring more energy
Why are Magnesium and Aluminum exceptions to the general trend of first ionization energy?
Magnesium has a higher first ionization energy because it has a complete s subshell while Aluminum has one valence electron in a p subshell making it easier to remove than Magnesium
Why are Phosphorus and Sulfur exceptions to the general trend of ionization energy?
Phosphorus has higher first ionization energy than sulfur because it has 3 half paired orbitals while sulfur has 1 paired orbital. It’s easier to remove a paired electron because of repulsion and so sulfur has a lower first ionization energy
Q) X has ionization energies: 500, 1100, 3000, 3900. Which group is it in?
It is in Group 2 because biggest jump is between 2nd and 3rd ionization energy so it likely has 2 valence electrons as it is harder to remove an electron from a stable configuration and one that’s closer to the nucleus
