Periodic Trends in Selected* Physical Properties of the Elements
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Periodic Trends in Selected* Physical Properties of the Elements (see pp. 91-98). Trend=> across a row. Trend=> down a column. * The usual suspects varied…. Covalent Atomic Radii, r First Ionization Potentials, I 1 Electron Affinities, E A. Covalent atomic radius, r , defined .

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Periodic Trends in Selected* Physical Properties of the Elements

(see pp. 91-98)

Trend=> across a row

Trend=> down a column

*The usual suspects varied…

  • Covalent Atomic Radii, r

  • First Ionization Potentials, I1

  • Electron Affinities, EA


Covalent atomic radius, Elementsr, defined

2r

Atoms of element are assumed to be spherical and `covalently’ bonded (no net charge on either atom) see also: p. 95, figure 2.35


First Ionization Potential, ElementsI1 defined (see also p.91)

I1 is the energy required to remove the first electron from an initially neutral element X

(The electron ejected is the easiest one to eject)

I1+ X  X+ + e-

Example: I1+ Li Li+ + e-

I1 in

2s

1s


Electron Affinity, ElementsEadefined (see p. 94)

Me want to bond with Li

 !!

Eais the energy released when an

electron is added to an initially neutral element X. (Because the system is losing

energy, Ea is < 0)

e-+ X  X- + Ea

Eaout

Example: e- + Li Li-

2s

1s


The estimated r for most of the elements Elements(crystallographic data)


What’s the trend for Elementsr across a row ?

?

Trend

down

a column ?

r decreasing…

r ~increasing

except…


Size decrease across a row reveals that not all electrons are created equal…

Ability of given electron type to neutralize (shield off) its nuclear proton follows the order:

s> p > d > f

The weaker the neutralization (shielding), the more powerful is the pull of the un-neutralized protons…which then pull the entire electron cloud closer in. (see p. 95)


The increase down a column compares the sizes of the same kind of orbital electrons…except that as we go down the column, the number of electrons increases. Hence, size should increase.

H 1s

Li [He] 2s

Na [Ne] 3s

K [Ar] 4s

Rb [Kr] 5s

Cs [Xe] 6s

1 e-

3 e-

11 e-

19 e-

37 e-

55 e-

Example: column 1- the alkali metals


U-Do-It Predictions… kind of orbital electrons…except that as we go down the column, the number of electrons increases. Hence, size should increase.

If you understand the reason for the trend in r, you can predict the trends in Ionization potential, I1and Electron Affinity, Ea

I1 trends ?? …and why

I1increases across..because protons pull harder on electrons, making them harder to remove

I1decreases down..because electrons are further away

As we move down making them easier to remove

??

??


U-Do-It Predictions… kind of orbital electrons…except that as we go down the column, the number of electrons increases. Hence, size should increase.

If you understand the reason for the trend in r, you can predict the trends in Ionization potential, I1and Electron Affinity, Ea

Eatrends ?? …and why

Eaincreases across..because protons pull harder on new electrons, which means a deeper potential well

Eadecreases down..because open orbits are further away

as we move down making them more shallow in potential

??

??


SUMMARY OF PERIODIC TRENDS kind of orbital electrons…except that as we go down the column, the number of electrons increases. Hence, size should increase.

R decreases

Ip increases

Ea increases

R increases

Ip decreases

Ea decreases


Exam 1 Headers and sample questions kind of orbital electrons…except that as we go down the column, the number of electrons increases. Hence, size should increase.

(Monday 23 September 2013)

  • 1.0. Introductions (3 pts)

  • What corporation did Doc Fong work at before becoming an impoverished chemistry professor?

  • __________________________________

Corning Inc.

  • 1.1 Atomic dimensions and scaling (6 pts)

  • What is the ~ratio of an electron orbit diameter to an atomic nucleus diameter?___________________

  • What is the ratio of proton to electron mass ? ______

  • If baseball (~2 inches across) is the nucleus the electrons would be

  • a) 10 feet away b) 300 miles away c) 3 miles away

100,000/1=105/1

~2000/1


  • 1.2 Element kind of orbital electrons…except that as we go down the column, the number of electrons increases. Hence, size should increase.Symbols and Names (18 pts)

  • Circle all the symbolic representations of atomic elements below that are incorrect: (must circle all for credit)

  • BB XetOyyy Cr

  • Write the correct name or symbol for the elements listed below: (1 pt for each correct answer) SPELLING MATTERS

  • Silver ____ Hg _________ potassium ___

  • How many neutrons are present in neutral Boron-11 ? __

mercury

K

Ag

6

11-5=6


1.4 Evolution of the Atomic Model ( 10 pts) kind of orbital electrons…except that as we go down the column, the number of electrons increases. Hence, size should increase.

1.3 Atomic Body Part Count (8 pts)

Mg

12

13

12

25-12=13

1.4. Evolution of the Atomic Model (10 pts)

a)Whose atomic model is this ?

Rutherford model

b)Which model doesn’t rely on theory at all ?

Spectroscopist’s atom


1.5. Wave and Planck’s Laws Calculations ( 9 pts) kind of orbital electrons…except that as we go down the column, the number of electrons increases. Hence, size should increase.

Given that *f = c=3*108 m/s

Calculate f given =10,000 m ____

Given E=hf= hc/ ; h=6.63*10-34 J*s c=3*108 m/s

Calculate E given f=3*107hz _______________

Calculate E given  =1*10-4 m _______________

f=3*108/10,000

=3*104=30,000 Hz

E=6.63*10-34*3*107 =1.989*10-26

f=c/=3*108/1*10-4 = 3*1012=>

E=6.63*10-34*3*1012=1.989*10-21J

1.6. Bohr’s Theory of the atom (4 pts)

Name two failures of the Bohr theory of the atom::

1) 2)

Couldn’t predict effect of magnet on H lines

Only good for H


1.7. Electronic Configurations of the Atoms (using the Periodic Table provided during exam) 22 pts

Write the complete electronic configurations for the elements below Mg _________________________________

Write the correct abbreviated electronic configurations for the elements below, making sure to pay attention to all the rules associated with d electrons if they are present.

P_______ Fe__________

Write the correct pigeonhole (orbital) diagrams for the elements below, making sure to pay attention to all the rules associated with d electrons if they are present, and including the correct inert gas core.

Cr_________________ Cu__________________________

1s22s22p63s2

[Ne]3s23p3

[Ar] 3d64s2

[Ar]


  • 1.8 Periodic Table provided during Periodic Table Predictions and Vocabulary (12 pts)

  • See mini-quiz 10

  • Chlorine is in this group column __________________

  • Example of an alkali metal__________________

halogens

Li,Na,K,Rb,Cs,Fr

  • 1.9 This, that and the other things (7 pts)

  • What experiment destroyed the old theory of light ? _____________________________

  • True or False

  • Bohr’s theory of the atom is good for all the elements. T F

Photoelectric effect experiment


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