1. AP Chemistry Due Next Class:
Trend presentations (more on this in a bit)
Upcoming Due Dates:
Ch. 6 Mastering Chemistry midnight)
Ch. 6 Adaptive follow-up midnight) **Extra credit

2. Warm up
Which element has an electron that experiences the highest effective nuclear charge? Be Mg Ca Sr

3. Lecture

4. Development of the Periodic Table
Dmitri Mendeleev and Lothar Meyer (1869) independently came to the same conclusion about how elements should be grouped.
Mendeleev’s table was based on atomic masses. It was the most fundamental property of elements known at the time.
About 35 years later, the nuclear atom was discovered by Ernest Rutherford.
Henry Moseley developed the concept of atomic number experimentally. The number of protons was considered the basis for the periodic property of elements.

5. Coulomb’s Law and Electron configurations
Coulomb’s Law to guide our thinking about relative magnitudes… we generalize this calling it “coulombic forces”
The greater the charges  the greater the force
The closer the charges  the greater the attraction
…the energy of atomic orbitals determines the stability of atoms and how atoms react.
𝐹= 𝑘 𝑄 1 𝑄 2 𝑑 2

6. Effective Nuclear Charge
Many properties depend on attractions between valence electrons and the nucleus.
Electrons are both attracted to the nucleus and repelled by other electrons. (shielding)
The coulombic forces an electron experiences depend on both factors.

7. Effective Nuclear Charge
The effective nuclear charge, Zeff, is found this way:
Zeff = Z − S
where Z is the atomic number and S is a screening constant, usually close to the number of inner electrons.

8. The shielding Effect (the screening effect)
The reduction of the full nuclear charge experienced by an outer electron as a result of screening by inner core electrons
Inner electrons always shield valence electrons, but valence electrons shield one another ineffectively.
The shielding effect arises from core electrons within the atom “screening” part of the nuclear (positive charge)

9. The effective nuclear charge felt by an atom’s valence electrons (X) going from left to right and (Y) going down a column on the periodic table.
X = increases Y = increases
X = increases Y = decreases
X = decreases Y = increases
X = decreases Y = decreases
Answer: a

10. Which element has an electron that experiences the highest effective nuclear charge?Be Mg Ca Sr

11. Which element has the largest number of screening electrons?Ba Mg Ca Sr

12. Effective Nuclear Charge Increases across a Period
What does each color represent?
What affects the effective nuclear charge?
Why does this make sense?

13. True or False: The large number of valence electrons in a chlorine atom greatly reduces the effective nuclear charge of the atom.
True
False
Answer: a

14. Periodicity
Repetitive pattern of a property for elements based on atomic number.
The following properties are discussed in this chapter:
Sizes of atoms and ions
Ionization energy
Electron affinity
Some group chemical property trends

15. Trend presentations
Use the rubric to guide your thinking
Use the Test Prep book to double check that you are including all good information
Think about the guided reading when making your notes sheet
Don’t be a wet blanket!
Group 1- Section 7.3 Atomic/Ionic Radius
Group 2- Section 7.4 Ionization Energy
Group 3- Section 7.5 Electron Affinity
Group 4- Section 7.7/7.8 Group Properties

16. Work time