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Model 2. Simulated Photoelectron Spectrum of Scandium

Model 2. Simulated Photoelectron Spectrum of Scandium

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ChemActivity 11



Electron Configurations and the Periodic Table



Model 3: The Periodic Table.

Note that the periodic table has an unusual form. The elements are arranged in

"blocks" of columns—a block of two columns on the left, six columns on the right, and

ten columns in the middle.



Critical Thinking Questions

4. What is the relationship between the form of the periodic table and the electron

configurations of the elements?



5. Based on the form of the periodic table, how many electrons is the 3d subshell

capable of holding?



6. Predict the electron configuration of Ga.



7. What is the common feature of the electron configurations of the elements in a

given column of the periodic table?



ChemActivity 11



Electron Configurations and the Periodic Table



67



Exercises

1. Identify the element whose simulated photoelectron spectrum is shown below:



IMPORTANT NOTE: In the above spectrum, the peak which arises from the 1s

electrons has been omitted.

2. Place the following in order of increasing energy to remove an electron from the 1s

energy level:

C



Pt



Ba



Ne



Zn



Gd



3. Make a rough sketch of the photoelectron spectrum of vanadium. Indicate the

subshell that gives rise to each peak and the relative height of each peak.

4. Provide the electron configuration for: P, P3–, Ba, Ba2+, S, S2–, Ni, Zn.

5. How many valence electrons does Ga have?



Problems

1. As atomic orbitals are filled, the 6p orbitals are filled immediately after which of

the following orbitals? 4f, 5d, 6s, 7s.

2+



3+



2. Provide the electron configuration for: Pd, Pd , Gd, Gd .



68



ChemActivity



12

Electron Spin

(Are Atoms Magnetic?)



Information

Experimental evidence suggests that the electrons in atoms can act like tiny magnets.

Because an electric charge spinning on an axis can produce a magnetic moment, this

property of electrons is called "spin." When a beam of hydrogen atoms is passed through

an inhomogeneous magnetic field (this is known as a Stern-Gerlach experiment), the

beam splits into two components of equal intensity, but deflected in opposite directions.

This implies that there are two equal and opposite magnetic moments possible for the

electron in the H atom, and that half of the atoms have one type and half of the atoms

have the other type. The electrons giving rise to these moments are often referred to as

"spin up" and "spin down."

When a beam of He atoms similarly undergoes a Stern-Gerlach experiment, the

beam passes through without being deflected. This implies that there is no magnetic field

associated with the He atoms, even though there are two electrons present. Thus, the two

electrons in the atom must have opposite spins—one "up" and one "down"—which

cancel each other out and provide no overall magnetic moment.



Model 1. The Electron Configurations of the Ground States

(lowest energy states) of Several Elements.



Critical Thinking Questions

1. What do the arrows in Model 1 represent?

2. What generalization can be made about 2 electrons in a "filled" s subshell?



ChemActivity 12



Electron Spin



69



3. For each case, predict the results of a Stern-Gerlach experiment on a beam of

atoms. That is, predict whether the atoms will pass through undeflected or will be

split into different components.

a) Li



b) Be



c) B



d) C



Model 2: Diamagnetic and Paramagnetic Atoms.

An atom with an equal number of spin "up" and spin "down" electrons is known as

diamagnetic, and the atom is repelled by a magnetic field. In this case we say that all of

the electrons are "paired." If this is not the case—that is, if there are unpaired electrons—

the atom is attracted to a magnetic field, and it is known as paramagnetic. The strength

of the attraction is an experimentally measurable quantity known as the magnetic

moment. The magnitude of the magnetic moment (measured in magnetons) is related to

(but not proportional to) the number of unpaired electrons present. That is, the larger the

number of unpaired electrons, the larger the magnetic moment.

Here are some simulated data concerning this phenomenon:

Table 1. Magnetic moments of several elements.

Element

Magnetic Moment

(magnetons)

H

Paramagnetic

1.7

He

Diamagnetic

0

B

Paramagnetic

1.7

C

Paramagnetic

2.8

N

Paramagnetic

3.9

O

Paramagnetic

2.8

Ne

Diamagnetic

0



Critical Thinking Questions

4. Why is the situation of equal numbers of spin up and spin down electrons referred

to as all the electrons being "paired"?



5. Based on the data in Table 1, rank the following atoms in terms of the number of

unpaired electrons in each atom: B, C, N, O, Ne. Explain your reasoning clearly.



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Model 2. Simulated Photoelectron Spectrum of Scandium

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