Trends in the periodic Trends in the periodic table:table:

Ionization EnergyIonization EnergyAtomic RadiusAtomic Radius

Electron AffinityElectron AffinityElectronegativityElectronegativity

BackgroundBackground• 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 energyIonization 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 Periodic table

trendstrends Answers Answers

Ionization energy vs. atomic numberIonization energy vs. atomic number

Ca

K

H

He

Li

B

Be C

N O

F

Ne

Na

MgAl

SiP S

Cl

Ar

0

500

1000

1500

2000

2500

0 2 4 6 8 10 12 14 16 18 20

Element

Ioni

zatio

n en

ergy

(kJ

/mol

)

Atomic radius vs. atomic numberAtomic radius vs. atomic number

Ca

K

H He

Li

B

Be

C N O FNe

NaMg

Al Si P S Cl

Ar

0

50

100

150

200

250

0 2 4 6 8 10 12 14 16 18 20

Element

Ato

mic

Rad

ius

(pm

)

AnswersAnswers2 a) – He, Ne, Ar, Noble gases2 b) – Li, Na, K, Alkali metals3 a) – Li, Na, K, Alkali metals3 b) – He, Ne, Ar, Noble gases4. As one increases, the other decreases5. Ionization energy increases

Atomic radius decreases6. Ionization energy decreases

Atomic radius increases

7.

11p+ 12n°

Na has 11 electrons

Na+ has 10 electrons

Ne has 10 electrons

11p+ 12n°

10p+ 10n°

electron configuration of Na+ resembles NeAlkali metals become like noble gases8. 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 ignored11.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

AnswersAnswers2 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)

7.

11p+ 12n°

Na has 11 electrons

Na+ has 10 electrons

Ne has 10 electrons

11p+ 12n°

10p+ 10n°

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)

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 Total: /24

Note: graphs from day 1 were marked separately

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