Ch.8 - Periodic Properties of the ElementsSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Trends in Ionization Energy

Concept #1: Understanding Ionization Energy

Ionization energy is the energy required to remove an electron from a gaseous element. 

Concept #2: Exceptions to Ionization Energy in Groups 5A & 6A

Concept #3: Exceptions to Ionization Energy in Groups 2A & 3A 

Example #1: Of the following atoms, which has the smallest second ionization energy?

Al                     Li                     Rb              Mg                  Be                    

Practice: Of the following atoms, which has the smallest third ionization energy?

Practice: Which of the following statements is/are true? 

a. Sulfur has a larger IE1 than Phosphorus 

b. Boron has a lower IE1 than Magnesium 

c. Magnesium has a higher IE1 than Aluminum

Practice: Shown below are the numerical values for ionization energies (IE's). Match the numerical values with each of the following elements provided in the boxes.

Additional Problems
What is the best explanation for the fact that the ionization energy of boron is lower than that of beryllium? 1. the quantum mechanical stability of the filled s subshell of beryllium 2. the increased repulsion experienced by the electrons in beryllium 3. boron has a larger effective nuclear charge than beryllium. 4. the radius of boron is smaller than that of beryllium making it easy to remove an electron
Write an equation that represents the second ionization energy of copper. 1. Cu+(g) → Cu2+(g) + e −  2. Cu(g) → Cu2+(g) + e − 3. Cu+(g) → Cu2+(g) + 2 e − 4. Cu(g) → Cu+(g) + e − 5. Cu(g) → Cu2+(g) + 2 e − 
Which of the following options correctly lists the provided atoms in order of the ease with which they lose electrons?  B     K     Na     He     H a) K < Na < B < He < H b) H < He < B < Na < K c) He < H < B < Na < K d) K < Na < B < H < He e) B < H < He < K < Na
The first three ionization energies for Ba is given in the graph below.  Explain this trend in terms of the electronic configuration; in particular, discuss why the third ionization energy is almost 4 times higher than the second.
An atom is found to have the following ionization energies (in kJ/mol) IE1 = 577; IE2 = 1816; IE3 = 2,744; IE4 = 11,576; IE5 = 18, 375 Which of the following is the most likely choice for this atom? A. Na B. Mg C. Al D. Si E. P
Which of the following contains the atoms listed in order of INCREASING ionization energy? A. Na < K < Rb B. O < N < C C. C < F < O D. C < O < F E. Ar < As < K
Which of the following elements has the largest ionization energy? A) Na B) Ne C) F D) K E) Rb
Which of the following correctly represents the second ionization of calcium? a. Ca (g) → Ca + (g) + e b. Ca + (g) → Ca 2+ (g) + e c. Ca - (g)  + e → Ca 2- (g) d. Ca + (g)  + e → Ca 2+ (g)  e. Ca + (g)  +  e → Ca (g)
Consider the following orderings. I. Al < Si < P II. Be< Mg< Ca III. I<Br< CI IV. Na+< Mg2+< Al3+ Which of the above gives a correct trend for increasing ionization energy for loss of one electron from the indicated atom or ion? A. II, IV B. I, III C. III, IV D. I, III, IV E. none of these are correct
What period 3 element has the following ionization energies (all in kJ/mol)? A) Si                             B) S                             C) P                             D) Cl                            E) Mg
Which do you expect to require more energy: removing the electron from a H atom, or removing the electron from a He+ ion?      Explain your reasoning using number or words. 
Of the choices below, which gives the order for first ionization energies? A) C l > S > Al > Ar > Si B) Ar > Cl > S > P > Al C) Al > Si > S > Cl > Ar D) Ar > Cl > S > Si > Al E) S > Si > Cl > Al > Ar
Rank these elements according to first ionization energy from highest to lowest. Mg  , Si  , S  , Cl  , Ar  , Na
Which of the following processes represents the ionization energy of iodine? a) I2 (s) → I2+ (g) + e b) I2 (g) → I2+ (g) + e c) I (s) → I + (g) + e d) I (g) → I + (g) + e e) I (l) → I + (l) + e
Which element will display a very large jump in ionization energy values between  I3, and I4, its third and fourth ionization energies? a) Na b) Mg c) Al d) Si e) P
Of the following atoms, which has the smallest second ionization energy? a) Be                            b) Al                             c) Li                             d) Ba                            e) In
Which of the following represents the  third ionization of Mn? Mn– (g) + e –  →  2 Mn2- (g) Mn2+ (g)  →  Mn3+ (g) + e – Mn2- + e –  →  Mn3- (g) Mn2+ (g)  →  Mn+ (g) + e –
Given the following successive ionization energies (1st, 2nd, 3rd ionization energies etc) what element do they correspond to? a. Li b. Be c. B d. C e. N
Helium has two electrons in the 1s orbital. When it becomes singly ionized, forming He+,  (A) its spectrum resembles that of the hydrogen spectrum.  (B) the remaining electron is easier to remove.  (C) the nuclear charge has decreased by one. (D) it has lost one atomic mass unit. 
Which pair of elements is listed in order of decreasing first ionization energy? a) Na, Mg b) Mg, Al c) Al, Si d) Si, P
Which of the atoms will have the smallest first ionization energy? (a) Helium (b) Strontium (c) Barium (d) Nitrogen (e) Fluorine
Arrange the elements in Mg, Ne, Na, and Ar in order of increasing energy required to remove the first electron from their atoms: a. Na < Mg < Ar < Ne b. Ne < Ar < Mg <Na c. Mg < Na < Ar <Ne d. Ar < Ne < Na < Mg
The first three ionization energies of an element X are 590, 1145 and 10,192 kJ/mol. What is the most likely formula for a stable ion of X? a. X + b. X 2+ c. X 3+ d. X -
For the successive ionization of an atom of Nitrogen, where would the first large increase in ionization energy be observed? A. Between E1 and E2 B. Between E2 and E3 C. Between E4 and E5 D. Between E5 and E6 E. Between E7 and E8
Which element will have the largest first ionization energy? A. Ca B. Mg C. Be D. Na E. K
The first three ionization energies of an element X are 590, 1145 and 10,912 kJ/mol. What is the most likely formula for a stable ion of X? a. X+ b. X2+ c. X3+ d. X4+
Which excited state molecule or ion will have the smallest ionization energy? a. H (2p1 ) b. He (1s13p1 ) c. Li (1s24p1) d. Be (1s22s15p1 ) e. B (1s22s26p1 )
Why does the ionization energy increase when electrons are consecutively removed from an atom? a. the outermost electron experiences a higher effective nuclear charge b. the remaining electrons are held more strongly c. atomic radius is decreasing d. all of the above e. none of the above
The process of removing an electron from a neutral element in the gas phase… a. requires energy for all elements, because the initial state is less stable than the final state. b. requires energy for all elements, because the initial state is more stable than the final state. c. does not require energy for any element, because the initial state is the same energy as the final state. d. requires energy for some elements, because sometimes the initial state is more stable than the final state.
Which of the following would be expected to have the lowest first ionization energy? 1. F 2. C 3. O 4. Ne 5. Li 
Which element would have the following ionization energies (listed in kJ/mol)? IE1     IE2      IE 3       IE 4       IE 5        IE 6 800   2430  3600  25,020  32,820   47,280 A. F B. O C. N D. C E. B
Circle that atom that is hardest to ionize: S       Te
Write a chemical equation representing the second ionization energy for lithium.
Which ionization process requires the most energy? Explain?a. W(g) → W+(g) + e-b. W+(g) → W2+(g) + e-c. W2+(g) → W3+(g) + e-d. W3+(g) → W4+(g) + e-
Identify an atom that has the following first five successive ionization energies: E1 = 801 kJ/mol        E2 = 2,427 kJ/mol E3 = 3,660 kJ/mol E4 = 25,026 kJ/mol E5 = 32,827 kJ/mol A. Be                 B. B               C. C                   D. N               E. O
Choose the element with the higher ionization energy for the following pair. As or Bi 
Choose the element with the higher ionization energy for the following pair. As or Br
Which reaction below represents the first ionization of O?a. O(g) + e- → O-(g)b. O+(g) + e- → O(g)c. O(g) → O+(g) + e-d. O-(g) + e- → O2-(g)e. O-(g) → O(g) + e-
Identify the element of Period 2 which has the following successive ionization energies, in kJ/mol. 
Which alkali metal has the highest ionization energy?
Write a chemical equation representing the second ionization energy for lithium. Use e- as the symbol for an electron.
Arrange the elements in decreasing order of first ionization energy. Rank from highest to lowest first ionization energy. To rank items as equivalent, overlap them. In, Ge, Se, Cs
Place the following in order of increasing IE1.K, Ca, Rb a. Rb < K < Ca b. Ca < Rb < K c. K < Ca < Rb d. Ca < K < Rb e. Rb < Ca < K
Comparing the ionization energies of chlorine, selenium and sulfur. a. S > Se and S = Cl. b. S > Se and S > Cl. c. S < Se and S < Cl. d. S > Se and S < Cl. e. S < Se and S = Cl.
Which of the following elements has the  smallest first ionization energy? a) P b) K c) C d) Mg e) Ar
Of the choices below, which gives the order for first ionization energies?a. Al > Si > S > Cl > Arb. S > Si > Cl > Al > Arc. Cl > S > Al > Ar > Sid. Cl > S > Al > Si > Are. Ar > Cl > S > Si > Al
Consider the following set of successive ionization energies:IE1 = 578 kJ/mol; IE2 = 1,820 kJ/mol; IE3 = 2,750 kJ/mol; IE4 =11,600 kJ/mol.To which third period element do these ionization values belong?a. Phosphorousb. Chlorinec. Scandiumd. Aluminume. None of the above
Which of the following is TRUE about first ionization energies? a. Na < Mg < Al b. Si < P < S c. Na > Si > Cl d. P > S < Cl e. None of the above
When the species F -, Na+, and Ne are arranged in order of increasing energy for the removal of an electron, what is the correct order?a) F - < Na+ < Neb) F - < Ne < Na +c) Na+ <Ne < F -d) Ne < F - < Na+
The first ionization potential of the elements B, C, and N (atomic numbers 5, 6, and 7) steadily increases, but that of O is less than that of N. The best interpretation of the lower value for O is that A. there is more shielding of the nuclear charge in O than in B, C, or N. B. the ionization potential of N is a maximum and the values decrease steadily for the elements O, F, and Ne. C. the half-filled set of p orbitals in N makes it more difficult to remove an electron from N than from O.  D. the electron removed from O is farther from the nucleus and therefore less tightly bound than that in N. E. the electron removed from O corresponds to a different value of the quantum number ℓ than that of the electron removed from B, C, or N.
Which property of the third period nonmetallic elements might be the one depicted in the graph?
Which ionization process requires the most energy?a. S(g) → S+(g) + e-b. S+(g) → S2+(g) + e-c. Cl(g) → Cl+(g) + e-d. Cl+(g) → Cl2+(g) + e-
Arrange the elements in order of decreasing first ionization energy. Rank from highest to lowest first ionization energy. To rank items as equivalent, overlap them.
Which graph shows the correct trend for ionization energies, IE, of aluminum, Al?
Rank these elements according to first ionization energy. 
Rank these elements according to first ionization energy (highest to lowest) :Ne, F, O, N, C, B, Be, Li
Write chemical equations for first ionization step of carbonic acid Write chemical equations for second ionization step of carbonic acid.
Consider the following set of successive ionization energies: IE1 = 1012kJ/mol IE2 = 1,920kJ/mol IE3 = 2,910kJ/mol IE4 = 5,000kJ/mol IE5 = 6,300kJ/mol IE6 = 21,220kJ/mol IE7 = 29,780kJ/mol To which third period element (enter the symbol or name) do these ionization values belong?
Rank these elements according to first ionization energy from highest to lowest. Mg - Si - S - Cl - Ar -Na
Which element has the highest ionization energy?a. Sr or Bab. Br or I or Te
The ionization energy of chlorine is lower than the ionization energy of _____.a. sodiumb. fluorinec. hydrogend. lithiume. calcium 
Arrange the following elements in order of decreasing first ionization energy Po, Cl, Te, and S. Rank elements from largest to smallest. 
Write a chemical equation representing the second ionization energy for lithium. Use e- as the symbol for an electron. 
Using only the periodic table arrange the following elements in order of increasing ionization energy: iodine, antimony, strontium, xenon