Trends in the periodic table:
Ionization Energy
Atomic Radius
Electron Affinity
Electronegativity
Background
• Electrons can jump between shells (Bohr’s
model supported by line spectra)
• The electrons can be pushed so far that they
escape the attraction of the nucleus
• Losing an electron is called ionization
• An ion is an atom that has either a net
positive or net negative charge
• Q: what would the charge be on an atom
that lost an electron? Gained two electrons?
• A: +1 (because your losing a -ve electron)
• A: -2 (because you gain 2 -ve electrons)
Ionization energy
• Ionization energy is the energy required to
remove one outer electron from an atom
• We will be examining the trends in ionization
energy in groups and periods
• Handout
• Note: atomic radius is the distance from the
nucleus to the outer electron shell
• Follow directions on sheet and answer
questions (you can use textbook for help)
• Ignore H when looking at trends, look at many
periods/groups when summarizing trends
Periodic table trends
Answers
Ionization energy vs. atomic number
He
Ionization energy (kJ/mol)
2500
Ne
2000
Ar
F
1500
N
H
Cl
C
Be
1000
O
P S
B
500
Mg Si
Al
Li
Ca
Na
K
0
0
2
4
6
8
10
12
Element
14
16
18
20
Atomic radius vs. atomic number
Atomic Radius (pm)
250
K
200
Na
Li
150
Mg
Al Si
Be
100
Ca
P S Cl
B C N
O F
Ar
Ne
50
H
0
0
He
2
4
6
8
10
12
Element
14
16
18
20
Answers
2 a) – He, Ne, Ar, Noble gases
2 b) – Li, Na, K, Alkali metals
3 a) – Li, Na, K, Alkali metals
3 b) – He, Ne, Ar, Noble gases
4. As one increases, the other decreases
5. Ionization energy increases
Atomic radius decreases
6. Ionization energy decreases
Atomic radius increases
7.
11p+
12n°
11p+
12n°
10p+
10n°
Na has 11
electrons
Na+ has 10
electrons
Ne has 10
electrons
electron configuration of Na+ resembles Ne
Alkali metals become like noble gases
8. Radius increases because shells are added
Increased radius will make it easier to lose an
electron because of greater distance between
positive and negative charges
9. Proton # increases. More protons means
greater attraction between nucleus and outer
electron thus higher ionization energy.
The greater attraction also means that outer
electrons are brought closer to the nucleus,
thus smaller atomic radius results.
Li (enc = 1)
++
+
Be (enc = 2)
++
+
+
B (enc = 3)
+++
++
10. Noble gases are ignored
11. Electron affinity is energy associated with an
atom gaining an electron. It is highest in the
top right where atoms are smallest with the
greatest number of protons
12. Electronegativity is a number that describes
the relative ability of an atom (when bonded)
to attract electrons. The trend is the same as
affinity for the same reason
Answers
2 a) – He, Ne, Ar (1), Noble gases (1)
2 b) – Li, Na, K (1), Alkali metals (1)
3 a) – Li, Na, K, Alkali metals (1)
3 b) – He, Ne, Ar, Noble gases (1)
4. As one increases, the other decreases (1)
5. Ionization energy increases (1)
Atomic radius decreases (1)
6. Ionization energy decreases (1)
Atomic radius increases (1)
/11
7.
11p+
12n°
11p+
12n°
10p+
10n°
Na has 11
electrons
Na+ has 10
electrons
Ne has 10
electrons
Diagram of Na(1) & Na+(1), Na+ resembles Ne (1)
Alkali metals become like noble gases (1)
8. Radius increases because shells are added (1)
Increased radius will make it easier to lose an
electron because of greater distance between
positive and negative charges (1)
/6
9. Proton # increases (1). More protons means
greater attraction between nucleus and outer
electron (1) thus higher ionization energy.
The greater attraction also means that outer
electrons are brought closer to the nucleus,
thus smaller atomic radius results.
Li (enc = 1)
++
+
Be (enc = 2)
++
+
+
B (enc = 3)
+++
++
10. Noble gases are ignored (1)
11. Electron affinity is energy associated with an
atom gaining an electron (1). It is highest in
the top right (1) where atoms are smallest with
the greatest number of protons
12. Electronegativity is a number that describes
the relative ability of an atom (when bonded)
to attract electrons (1). The trend is the same
as affinity (1) for the same reason
9 – 10: /7
Total:
/24
Note: graphs from day 1 were marked separately
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