1. Section 3: Periodic Trends

2. Atomic Radius decreases Atomic Radius increases
Periodic Trends
Atomic Radius decreases
Can you explain in terms of nuclear charge & shielding
Atomic Radius increases

3. Atomic Radius decreases Atomic Radius increases
Periodic Trends
Atomic Radius decreases
Ionization Energy ???
Electronegativity ???
Electronegativity ???
Ionization Energy ???
Atomic Radius increases

4. + WHY? Ionization Energy (IE): energy required to remove an e–
Down a Group:
decreases ↓
Across a Period:
WHY?
increases ↑
Figure: 07-10
Title:
First ionization energy versus atomic number.
Caption:
The red dots mark the beginning of a period (alkali metals), the blue dots mark the end of a period (noble gases), and the black dots indicate other representative elements. Green dots are used for the transition metals.

5. increases across a period
First IE Trends +
increases across a period
-due to greater nuclear charge
(more attraction)
-due to
more
shielding
(less attraction)
decreases down a group

6. Example of Ionization Energy Trend
Arrange in order of increasing first ionization energy: Mg, Na, Si, Al
Na < Mg < Al < Si

7. Electronegativity (EN) Trends
atom’s ability to attract bonded e–’s
increases across a period
-due to greater nuclear charge
(more attraction)
-due to
more
shielding
(less attraction)
decreases down a group

8. Example of Electronegativity Trend
Arrange the following elements in order of increasing electronegativity: B, Na, F, O
Na < B < O < F

9. Overall Reactivity
Reactivity tells you how likely or vigorously atoms will react with each other.
Trend for Metals:
decreases across a period due to increased nuclear charge
increases down a group due to more shielding

10. Overall Reactivity
Reactivity tells you how likely or vigorously atoms will react with each other.
Trend for Metals:
The most reactive metals lose electrons the most easily (they are good electron donors)

11. Overall Reactivity
Reactivity tells you how likely or vigorously atoms will react with each other.
Trend for Non-Metals:
increases across a period due to increased nuclear charge
decreases down a group due to more shielding

12. Overall Reactivity
Reactivity tells you how likely or vigorously atoms will react with each other.
Trend for Non-Metals:
The most reactive nonmetals gain electrons the most easily (they are good electron takers)

13. Overall Reactivity

14. Periodic Trends (Summary)
Atomic Radius decreases
Ionization Energy increases
Electronegativity increases
Can you explain all of this in terms of p’s and e’s?
nuclear charge
shielding
Electronegativity decreases
Ionization Energy decreases
Atomic Radius increases

15. Quick Quiz!
As you go across period 3 from Na to Ar, the energy needed to remove an electron from an atom ______________.
A. decreases due to greater nuclear charge
B. decreases due to less shielding
C. increases due to greater nuclear charge
D. increases due to less shielding

16. Quick Quiz.
IE: 500 kJ
1500 kJ
Alkali metals have lower ionization energies than noble gases because _____________.
A. alkali metals are smaller with more protons.
B. noble gases are larger with more protons.
alkali metals are larger with lower
nuclear charges.
D. noble gases are smaller with fewer protons.

17. Quick Quiz.
Fluorine is the most electronegative element because it has ____________.
A. more nuclear charge and more shielding
B. less nuclear charge and more shielding
C. more nuclear charge and less shielding
D. less nuclear charge and less shielding

18. Periodic Trends (Summary)
Atomic Radius decreases
Ionization Energy increases
Electronegativity increases
Can you explain all of this in terms of p’s and e’s?
nuclear charge
shielding
Electronegativity decreases
Ionization Energy decreases
Atomic Radius increases