1. MS. SAMAYOA BIRMINGHAM COMMUNITY CHARTER HIGH SCHOOL CHEMISTRY
PERIODIC TRENDS
MS. SAMAYOA
BIRMINGHAM COMMUNITY CHARTER HIGH SCHOOL
CHEMISTRY

2. Learning Objective: Students will be able to explain periodic trends by studying the atomic radius, ionization energy, and electronegativity from a table Academic Vocabulary: Atomic radius, ionization energy, and electronegativity

3. ATOMIC RADIUS Atomic radius is the radius of an atom
The distance from the atomic nucleus to the outermost stable electron orbital in an atom

4. Atomic radius
What happens to the atomic radius when we go across a period?
Decreases
What happens to the atomic radius when we go down a group?
Increases
BUT WHY?

5. Let’s do some research HAVE TO KNOW:
Protons have a positive charge (+)
Electrons have a negative charge (-)
Positive and negative are ATTRACTED TO EACH OTHER

6. ACROSS A PERIOD: FILL OUT THE FOLLOWING CHART USING THE PERIODIC TABLENa Mg Al Si P S Cl Ar
# of shells
# of protons
Atomic Radius
(picometers)
166
141
121
111
107
105
102
106
Ionization Energy (kJ/mole)
496
738
578
787
1012
1000
1251
1521
Electronegativity (4 point scale)
0.9
1.2
1.5
1.8
2.1
2.5
3.0
---

7. Down a group: fill out the chart using the periodic table
# of shells
# of protons
Atomic Radius (picometers)
Ionization Energy (kJ/mole)
Electronegativity
(4 point scale) H 31
1312
2.1 Li
128
520
1.0 Na
166
496
0.9 K
203
410
0.8 Rb
220
403 Cs
244
376
0.7

8. ATOMIC RADIUS ACROSS A PERIODNa Mg Al Si P S Cl Ar
# of shells 3
# of protons 11 12 13 14 15 16 17 18
Atomic Radius
(picometers)
166
141
121
111
107
105
102
106
Ionization Energy (kJ/mole)
496
738
578
787
1012
1000
1251
1521
Electronegativity (4 point scale)
0.9
1.2
1.5
1.8
2.1
2.5
3.0
---
Noble gases have only van der waals radii because it cannot have covalent bonds with other elements
Other elements can have covalent bonds with other elements
As the number of protons increase, the atomic radius decreases.

9. THINK ABOUT IT…
Why is it when the number of protons increase, the atomic radius decreases?

10. ATOMIC RADIUS DOWN A GROUP
# of shells
# of protons
Atomic Radius (picometers)
Ionization Energy (kJ/mole)
Electronegativity
(4 point scale) H 1 31
1312
2.1 Li 2 3
128
520
1.0 Na 11
166
496
0.9 K 4 19
203
410
0.8 Rb 5 37
220
403 Cs 6 55
244
376
0.7
As the number of shells
increases, the atomic radius increases

11. THINK ABOUT IT…
Why is it that when the number of shells increase, the atomic radius increases?

12. Ionization energy
Ionization energy is the amount of energy required to remove an electron

13. Let’s do some research HAVE TO KNOW:
Protons have a positive charge (+)
Electrons have a negative charge (-)
Positive and negative are ATTRACTED TO EACH OTHER

14. Ionization energy: across a periodNa Mg Al Si P S Cl Ar
# of shells 3
# of protons 11 12 13 14 15 16 17 18
Atomic Radius
(picometers)
166
141
121
111
107
105
102
106
Ionization Energy (kJ/mole)
496
738
578
787
1012
1000
1251
1521
Electronegativity (4 point scale)
0.9
1.2
1.5
1.8
2.1
2.5
3.0
---
As the number of protons increase, the ionization energy increases

15. Why is it that when the number of protons increases, the ionization energy increases across a period?

16. Ionization energy: down a group
# of shells
# of protons
Atomic Radius (picometers)
Ionization Energy (kJ/mole)
Electronegativity
(4 point scale) H 1 31
1312
2.1 Li 2 3
128
520
1.0 Na 11
166
496
0.9 K 4 19
203
410
0.8 Rb 5 37
220
403 Cs 6 55
244
376
0.7
As the number of shells increase, the ionization energy decreases

17. Why is it that when the number of shells increases, the ionization energy decreases?

18. ELECTRONEGATIVITY
Electronegativity is the power of an atom in a molecule to attract electrons to itself

19. ACROSS A PERIOD: ELECTRONEGATIVITYNa Mg Al Si P S Cl Ar
# of shells 3
# of protons 11 12 13 14 15 16 17 18
Atomic Radius
(picometers)
166
141
121
111
107
105
102
106
Ionization Energy (kJ/mole)
496
738
578
787
1012
1000
1251
1521
Electronegativity (4 point scale)
0.9
1.2
1.5
1.8
2.1
2.5
3.0
---
As the number of protons increases, the electronegativity increases

20. Why is it when the number of protons increases, the electronegativity increases?

21. DOWN A GROUP: ELECTRONEGATIVITY
# of shells
# of protons
Atomic Radius (picometers)
Ionization Energy (kJ/mole)
Electronegativity
(4 point scale) H 1 31
1312
2.1 Li 2 3
128
520
1.0 Na 11
166
496
0.9 K 4 19
203
410
0.8 Rb 5 37
220
403 Cs 6 55
244
376
0.7
As the number of shells increases, the electronegativity decreases

22. Why is it that when number of shells increases, the electronegativity decreases?