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Wize University Chemistry Textbook > Periodic Table Trends

Ionization Energy

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Ionization Energy (IE)

The ionization energy is the amount of energy required to remove the outermost electron from an atom or ion in the gas phase
  • If removing an electron do we get an anion or a cation?
    cation

E→E++e−ΔE=Ionization Energy\textbf{E}\mathbf{\rightarrow}\textbf{E}^\mathbf{+}\mathbf{+}\textbf{e}^\mathbf{-}\quad\quad\Delta\text{E}=\text{Ionization Energy}
  • ↑IE means that the atom/ion requires more energy for a valence electron to be removed (has a tight pull on electron)


The Periodic Trend
  • As we move to the right across a period, Zeff increases and the electrons are held more tightly. Therefore, it takes more energy to remove an electron and the IE increases as we move to the right.

  • As we move down a group and the valence electrons are further away from the nucleus, they are held more weakly (lower Zeff) and IE decreases (it becomes easier to remove the outermost electron)




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Comparing 1st, 2nd, and 3rd Ionization Energies


How does the first IE compare to the second IE?


First Ionization Energy (IE1):    A (g)  →  A+ (g)  +  e−First\ Ionization\ Energy\ \left(IE_1\right):\ \ \ \ A\ \left(g\right)\ \ \rightarrow\ \ A^+\ \left(g\right)\ \ +\ \ e^-

Second Ionization Energy (IE2):    A+ (g)  →  A2+ (g)  +  e−Second\ Ionization\ Energy\ \left(IE_2\right):\ \ \ \ A^+\ \left(g\right)\ \ \rightarrow\ \ A^{2+}\ \left(g\right)\ \ +\ \ e^-

Third Ionization Energy (IE3):    A2+ (g)  →  A3+ (g)  +  e−Third\ Ionization\ Energy\ \left(IE_3\right):\ \ \ \ A^{2+}\ \left(g\right)\ \ \rightarrow\ \ A^{3+}\ \left(g\right)\ \ +\ \ e^-

1st ionization is always smaller than the 2nd because removing a negatively charged electron from a cation is more difficult.
Example:
Ca (g)  →  Ca+ (g)  +  e−    IE1 = 590 kJmolCa\ \left(g\right)\ \ \rightarrow\ \ Ca^+\ \left(g\right)\ \ +\ \ e^-\ \ \ \ IE_1\ =\ 590\ \frac{kJ}{mol}

Ca+ (g)  →  Ca2+ (g)  +  e−    IE2 = 1145 kJmolCa^+\ \left(g\right)\ \ \rightarrow\ \ Ca^{2+}\ \left(g\right)\ \ +\ \ e^-\ \ \ \ IE_2\ =\ 1145\ \frac{kJ}{mol}


Wize Tip
IE1 < IE2 < IE3 < IE4 etc


How does the IE2 and IE3 for magnesium compare?




A core electron is much more difficult to remove than a valence electron, for example: the 3rd ionization energy of magnesium is much, much, higher than the 2nd.

Wize Tip
Although the IE increases each time another electron is removed, the increase is not linear and is usually related to the electron configuration.

Ionizing Mg2+ would be very difficult!
Mg→  Mg+ +  e−    IE1 = 738 kJmolMg\rightarrow\ \ Mg^+\ +\ \ e^-\ \ \ \ IE_1\ =\ 738\ \frac{kJ}{mol}

Mg+→  Mg2+ +  e−    IE2 = 1451 kJmolMg^+\rightarrow\ \ Mg^{2+}\ +\ \ e^-\ \ \ \ IE_2\ =\ 1451\ \frac{kJ}{mol}

Mg2+→  Mg3+ +  e−    IE3 = 7733 kJmolMg^{2+}\rightarrow\ \ Mg^{3+}\ +\ \ e^-\ \ \ \ IE_3\ =\ 7733\ \frac{kJ}{mol}


Needing so much energy to remove the 3rd electron indicates that when 2 were removed it was stable/unstable:
stable
!


Practice: Highest 1st Ionization Energy

Which of the following species has the highest 1st ionization energy?


Practice: Trends in Ionization Energy

Rank the following atoms in order of increasing first ionization energy (1 = smallest; 6 = largest): Fe, O, Ba, Si, V, Zr


Fe
O
Ba
Si
V
Zr

Practice: Lowest Ionization Energy

Select the element with the lowest 3rd ionization energy.



Extra Practice
Periodic Trends: Ionization Energy
Choosing from the following elements answer the following questions. K, Ca, N, Ar, F
Which as the greatest second ionization energy?
Periodic Trends: Ionization Energy
Choosing from the following elements answer the following questions. K, Ca, N, Ar, F
Which has the largest first ionization energy
Periodic Trends: Ionization Energy
Choosing from the following elements answer the following questions. K, Ca, N, Ar, F
Which has the smallest 1st ionization energy?
Molecular Orbital Theory
Choose the correct option:
Ionization Energy, Electronic Configuration
Compare the 3rd IE of Ca, Sr and Y.
To which third period (row) element do these ionization values belong?
IE1= 578 kJ/mol IE2= 1820 kJ/mol IE3= 2750 kJ/mol IE4= 11600 kJ/mol
Periodic Trends: Ionization energy
Ionization Energy refers to the amount of energy require to do what?
IE
Identify the elements with highest and lowest IE: B, Al, C, or Si
IE
Rank the following according to increasing first ionization energy: Ne, Na, P, Ar, K.
Ionization Energy
a. Arrange the following elements in order of increasing IE1: Si, In, F, N.
b. Arrange the following elements in order of decreasing IE1: Br, Sb, Sn, N.
Ionization Energy
Consider the set of successive ionization energies:
IE1 = 540 kJ / mol; IE2 = 1430 kJ / mol; IE3 = 2628 kJ / mol; IE4 = 4200 kJ / mol; IE5 = 15700 kJ / mol;
Which element can these values correspond to if the element is in a. period 3, b. period 4?
Electronic Transition
What is the 4th ionization energy of Be?
MO Theory
Choose the correct statement.
MO Theory
Rank the following species in decreasing order of IE1:
He, O, He2+, O22+.
Ionization Energy
Which of the following statements are true regarding the second ionization energy (IE2) of calcium (Mg) vs potassium (Na).
Ionization Energy
Rank the following atoms in terms of increasing ionization energy (1 = smallest, 5 = largest).
Ionization Energy
Which of the following statements are true regarding the second ionization energy (IE2) of calcium (Ca) vs potassium (K).
Ionization Energy
A student has an exam question asking which has the higher first ionization energy, beryllium or boron. They answer boron, because based on Periodic Trends, boron is further to the right and hence will have the higher ionization energy; however, the answer is beryllium. Why?
Ionization Energy
Rank the following atoms in terms of increasing ionization energy (1 = smallest, 5 = largest).
Periodic trends: Second Ionization Energy
Which of the following correctly represents the second ionization energy of beryllium?
Periodic Trends: Comparing Ionization Energies
Which one of the following statements are true for the first ionization energy (IE1) of aluminum (Al) vs the IE1 of silicon (Si).
Periodic Trends: Ionization Energy
Rank the following atoms in order of increasing first ionization energy (1 = smallest; 6 = largest): Fe, O, Ba, Si, V, Zr
Periodic Trends: Ionization Energy
Which element from the ones shown below has the highest first ionization energy?
Periodic Trends: Ionization Energy
Choosing from the following elements answer the following questions. K, Ca, N, Ar, F
Which as the greatest second ionization energy?
Periodic Trends: Ionization Energy
Choosing from the following elements answer the following questions. K, Ca, N, Ar, F
Which has the largest first ionization energy
Periodic Trends: Ionization Energy
Choosing from the following elements answer the following questions. K, Ca, N, Ar, F
Which has the smallest 1st ionization energy?
Which element from the ones shown has the highest 2nd ionization energy? (IE2)
Periodic Trends: Ionization Energy
To which third period (row) element do these ionization values belong?
IE1= 578 kJ/mol IE2= 1820 kJ/mol IE3= 2750 kJ/mol IE4= 11600 kJ/mol
Periodic Trends: Ionization Energy
Which of the following has the largest second ionization energy for each of the following sets?
"The Periodic Table", image retrieved from Chemistry 2e (https://d3bxy9euw4e147.cloudfront.net/oscms-prodcms/media/documents/Chemistry2e-OP_QCzV58S.pdf) by Flowers, P et al., is licensed under CC BY.
Periodic Trends: Ionization Energy
Which of the following has the highest second ionization energy?
"The Periodic Table", image retrieved from Chemistry 2e (https://d3bxy9euw4e147.cloudfront.net/oscms-prodcms/media/documents/Chemistry2e-OP_QCzV58S.pdf) by Flowers, P et al., is licensed under CC BY.
Rank the following elements by increasing first ionization Energy:
O, Ge, Sc, Ba
"The Periodic Table", image retrieved from Chemistry 2e (https://d3bxy9euw4e147.cloudfront.net/oscms-prodcms/media/documents/Chemistry2e-OP_QCzV58S.pdf) by Flowers, P et al., is licensed under CC BY.
Rank the following species from lowest to highest 2nd Ionization energies :
F, C, Ga, Fe, Mg, K
"The Periodic Table", image retrieved from Chemistry 2e (https://d3bxy9euw4e147.cloudfront.net/oscms-prodcms/media/documents/Chemistry2e-OP_QCzV58S.pdf) by Flowers, P et al., is licensed under CC BY.
Periodic Trends:: Ionization Energy
Which of the following has the lowest ionization energy?
"The Periodic Table", image retrieved from Chemistry 2e (https://d3bxy9euw4e147.cloudfront.net/oscms-prodcms/media/documents/Chemistry2e-OP_QCzV58S.pdf) by Flowers, P et al., is licensed under CC BY.
Rank the following atoms/ions in order of increasing ionization energy: Ca, O, Te, Ne, O-.
Periodic Trends: Ionization Energy
Which of the following atoms is the following successive ionization energy data for?
Third ionization energy (IE3) = 2912 kJ/mol
Fourth ionization energy (IE4) = 4956 kJ/mol
If A > B means that the ionization energy of A is greater than the ionization energy of B then which of the following is INCORRECT?
Periodic Trends: Ionization Energy Exception
Contrary to what we would predict based on Zeff the Ionization Energy of aluminum is actually less than magnesium.This is because,
If A > B means the first ionization energy (I1) of A is greater than the first ionization energy of B, then which of the following comparisons is INCORRECT?
Periodic Trends: Lowest Ionization Energy
Select the element with the lowest 3rd ionization energy.
Periodic Trends
Which species should have the highest ionization energy?
Periodic Trends
Which group of the periodic table can most easily donate an electron in a chemical reaction?
Choose the answer below which correctly ranks the following elements in order of decreasing ionization energy: Cr, As, N, Sr, F
Periodic Trends: Ionization Energy
Which of these elements has the highest third ionization energy?
Periodic trends: Ionization Energy
Rank the following elements by increasing first ionization Energy: Si, Mn, O, K, F
Periodic Trends: Ionization Energy
Rank the following elements from smallest to greatest ionization energy: O, Al, Ca, Cs,
Ni.
Periodic Trends: Ionization Energy
Rank the following elements in increasing order of ionization energy: Al, F, Pd, Rb, Zr
Rb
<
Zr
<
Pd
<
Al
<
F
Atom: Atomic Properties
Students in a previous year were asked a certain set of questions. For each of the questions and the given responses, in the corresponding boxes, identify whether the student response is correct or incorrect and the corrections that need to be made.
a) Question: IE for O = 1310 kJ/mol and IE for Cl = 1250 kJ/mol. Explain why this difference exists.
Student’s response: Because Cl has a higher n-value the electrons are further from the nucleus, giving the atom more room and the ability to add additional electron(s).
like Winter 2015 MT1
Which equation describes the first ionization energy of Bromine?