1. Bell Ringer Write the electron configuration of the Oxygen anion
Write a set of quantum numbers for Chromium.

2. Week in Chemistry Day Topic Monday Periodic Trends Tuesday
Go over lab notebooks, Periodic Trends
Wednesday
Comprehensive quiz Unit 3
Thursday
Test Review
Friday
Unit 3 Test

3. Lab Notebooks

4. Coulomb’s Law

5. 4 factors that cause the trends
1. Nuclear Pull (Z) – the number of protons
Positive protons pull negative electrons
The protons pull on the outer electrons. The more protons, the more pull exerted by the nucleus on the outer electrons.

6. 4 factors that cause the trends
Electron repulsion – size of e- cloud
Electrons are negative and push away from each other
The more electrons in
an atom’s electron
cloud, the more they
are pushed away from
each other (due to having
the same charge), making
a bigger cloud.

7. 4 factors that cause the trends
3. Shielding electrons – all inner e- shield the valence electrons from nuclear pull
Number of energy levels

8. 4 factors that cause the trends
4. Zeff – the “effective” nuclear pull on outer electrons. The nuclear pull taking into account the shielding electrons which are taking most of the force.
Zeff= # protons - # non-valence electrons
Which element has more effective nuclear pull?
Fluorine
Magnesium OR

9. Atomic Radius Trend Draw it!
Increases down a column because the valence electrons are in a farther energy level (higher energy)
Decreases across a period because the nuclear pull is increasing and pulling the energy levels in.
Atomic Size DECREASES
Draw it!
Atomic Size INCREAES

10. Ionization Energy The energy needed to pull an electron from an atom.
The greater the ionization energy, the more difficult it is to remove an electron.

11. Ionization Energy DECREASES
Decreases down a group because there are more shielding electrons, so it takes LESS ENERGY to “steal” an electron.
Increases across a period because the nuclear pull on those electrons is increased with no extra shielding, so it takes MORE ENERGY to get the electrons away.
Ionization Energy INCREASES
Draw it!
Ionization Energy DECREASES

12. Electronegativity DECREASES
The ability of an atom to take an electron from another atom (wanting to gain an electron)
Decreases down a group because there are more
electrons to shield the nucleus (which does the
pulling)
Increases across a period because of increased Z
(nuclear pull)
Electronegativity
INCREASES
Draw it!
Electronegativity DECREASES

13. Trend
What is it?
Trend across a period
Trend down a group
What causes trend?
Atomic Radius
Size of atom
Decrease
Increase
nuclear pull
increased
More energy levels
Ionization Energy
Energy to remove electron
Nuclear pull increased
Less pull more shielding (bigger)
Electronegativity
Wanting to gain an electron
Closer to full outer ring/ nuclear pull

14. Ionic Size Metals lose electrons (form cations)
less e- repulsion, smaller e- cloud, smaller size
Nonmetals gain electrons (form anions)
more e- repulsion, larger e- cloud, larger size

15. Practice
1) Which is the smallest ion? Explain Na+ Cl- P3- 2) Which has the highest electronegativity? Explain. As Sn S 3) In the following pairs, which has the larger atomic radius? Explain. Mg or Ba Cu or Cu2+ S or S2- 4) In the following pairs, which has the higher ionization energy? Explain. Li or Cs Ca or Br

16. Periodic Trends Packet Practice

17. Exit Ticket Which element has a smallest ionic radius?
Which element has a largest ionic radius?
Which element requires the least amount of energy to remove a valence electron?