Ch.8 - Periodic Properties of the ElementsWorksheetSee 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 Electron Affinity

Concept #1: Understanding Electron Affinity

Electron affinity is the energy required to add 1 mole of electrons to a gaseous element. 

Example #1: Rank the following elements in order of increasing electron affinity. 

Cs, Hg, F, S

Se, S, Si

Practice: Shown below are the numerical values for electron affinities (EA's). Match the numerical values with each of the following elements provided in the boxes.

Additional Problems
Electron affinity corresponds to the energy released or absorbed in which process (for atom A)? 1. A → A+ +2e– 2. A + e– → A– 3. None of these 4. A 50 electron volt electron collides with A to give A + + 2e– 5. A → A+ + e–
The electron affinities of the following 4th row elements have the following values: K + e - →  K -1       EA = -48 kJ/moles Ca + e - →  Ca -1   EA = -4 kJ/moles  Ga + e - →  Ga -1   EA = -30 kJ/moles From the standpoint of the electron configuration of the atoms, explain this trend, in particular, why Ca is a small exothermic value.
The electron affinity value expected for the reaction Kr(g) + e → Kr -(g)  would be a) a large negative number b) a small negative number c) zero d) greater than that for Ar(g) e) meaningless because Kr already has a stable noble gas configuration
Which reaction below represents the electron affinity of Li? A) Li(g) + e- → Li -(g) B) Li(g) → Li+(g) + e- C) Li+(g) + e- → Li(g) D) Li+(g) → Li(g) + e- E) Li(g) + e- → Li+(g)
Which one of the following atoms has the least tendency to gain another electron? a) Neon b) Oxygen c) Chlorine d) Sodium e) Hydrogen
Which of the following elements has the greatest (most exothermic) electron affinity? a. Rb b. C c. Li d. Na e. Br
Which reaction below represents the electron affinity of O? A. O (g) + e - → O - (g) B. O (g) → O + (g) + e - C. O (g) + e - → O + (g) D. O + (g) → O (g) + e - E. O + (g) + e- → O(g)
Electron affinity corresponds to the energy released or absorbed in which process (for atom A)? 1. A → A + + 2 e – 2. A + e – → A + 3. None of these 4. A 50 electron volt electron collides with A to give A + + 2e –. 5. A → A + + e –
Which reaction below represents the  second electron affinity of S? (A) S(g) + e- → S-(g) (B) S-(g) + e- → S2-(g) (C) S(g) → S(g) + e- (D) S-(g) → S(g) + e- (E) S2-(g) → S-(g) + e-
Use the trends in ionization energy and electron affinity to explain why sodium chloride has the formula NaCl and not Na2Cl or NaCl2.
In April 2010, a research team reported that it had made Element 117. This discovery was confirmed in 2012 by additional experiments.Estimate a value for its electron affinity based on its position in the periodic table.
Figure Electron affinity in kJ/mol for selected s - and p-block elements.Why are the electron affinities of the Group 4A elements more negative than those of the Group 5A elements?
What is electron affinity?
What are the observed periodic trends in electron affinity?
The following table gives the electron affinities, in kJ/mol, for the group 1B and group 2B metals.Why do the electron affinities of the group 1B elements become more negative as we move down the group? [Hint: Examine the trends in the electron affinity of other groups as we proceed down the periodic table.] Cu -119 Zn >0 Ag -126 Cd >0 Au -223 Hg >0
The first ionization energy and the electron affinity of Ar are both positive values.What is the significance of the positive value in each case?
The first ionization energy and the electron affinity of Ar are both positive values.What are the units of electron affinity?
Choose the element with the more negative (more exothermic) electron affinity from each of the following pairs.Na or Rb
Choose the element with the more negative (more exothermic) electron affinity from each of the following pairs.B or S
Choose the element with the more negative (more exothermic) electron affinity from each of the following pairs.C or N
Choose the element with the more negative (more exothermic) electron affinity from each of the following pairs.Li or F
Compare the elements bromine and chlorine with respect to the following properties.electron affinity
Hydrogen is an unusual element because it behaves in some ways like the alkali metal elements and in other ways like nonmetals. Its properties can be explained in part by its electron configuration and by the values for its ionization energy and electron affinity.Explain why the electron affinity of hydrogen is much closer to the values for the alkali elements than for the halogens.
The electron affinity of each group 7A element is more negative than that of each corresponding group 6A element. Use the electron configurations to explain why this is so.
You may want to reference (Pages 273 - 273) Section 7.5 while completing this problem.If the electron affinity for an element is a negative number, does it mean that the anion of the element is more stable than the neutral atom?
Would a neutral K atom or a K+ ion have a more negative value of electron affinity?
Despite the fact that adding two electrons to O or S forms an ion with a noble gas electron configuration, the second electron affinity of both of these elements is positive. Explain.
Use the trends in ionization energy and electron affinity to explain why calcium fluoride has the formula CaF2 and not Ca2F or CaF.
The lightest halogen is also the most chemically reactive, and reactivity generally decreases as you move down the column of halogens in the periodic table. Explain this trend in terms of periodic properties.
Consider the first ionization energy of neon and the electron affinity of fluorine.These two quantities have opposite signs. Which will be positive, and which will be negative?
Consider the first ionization energy of neon and the electron affinity of fluorine.Would you expect the magnitudes of these two quantities to be equal? If not, which one would you expect to be larger?
Consider the first ionization energy of neon and the electron affinity of fluorine.Write equation for the electron affinity of fluorine.
Which element has the highest first electron affinity?a. Ob. Mgc. Nad. Ne
Which element has the highest (most negative) electron affinity?a. Xeb. Sc. Csd. Bae. Cu
What are the observed periodic trends in electron affinity? Check all that apply.a. For main-group elements, electron affinity generally becomes more negative as you move to the right across a rowb. For main-group elements, electron affinity generally becomes more positive as you move to the right across a rowc. There is not a corresponding trend in electron affinity going right across a rowd. For main-group elements, electron affinity generally becomes more negative as you move down a columne. For main-group elements, electron affinity generally becomes more positive as you move down a columnf. There is not a corresponding trend in electron affinity going down a column
Rank these elements according to electron affinity from most energy released by gaining an electron to most energy absorbed by gaining an electron. Si, Kr, Cl
Which halogen has the lowest electron affinity?
Which equation correctly represents the first electron affinity (EA 1) of calcium? a. Ca(g) + e–  →  Ca–(g) b. Ca(g) →  Ca+(g) + e– c. Ca+(g) + e– → Ca(g) d. Ca(g) →  Ca–(g) + e– e. Ca–(g) → Ca(g) + e–
Rank these elements according to electron affinity.  
Which of the following atoms has the  highest (most negative) electron affinity? a) Na b) Cl c) Br d) S e) As
Rank the following elements by electron affinity, from most positive to most negative EA value. To rank items as equivalent, overlap them. Fluorine, Selenium, Arsenic, Potassium, Argon
Arrange the following elements from greatest to least tendency to accept an electron. To rank items as equivalent, overlap them. Br, Se, Ge, Ca, K
Arrange the following elements from greatest to least tendency to accept an electron: F, Li, C, O, Be
The elements of which group in the periodic table release the most energy by gaining an electron? a. 1A b. 2A c. 3A d. 4A e. 5A f. 6A g. 7A h. 8A
The elements of which group in the periodic table absorb the most energy when gaining an electron? a. 1A  b. 3A c. 4A d. 5A e. 6A f. 7A g. 8A
For each of the following pairs of elements:(Mg and K)     (F and Cl)pick the atom with the more favorable (more negative) electron affinity.
The electron affinities of the elements from aluminum to chlorine are -44, -120, -74, -200.4, and -384.7 kJ/mol, respectively. Rationalize the trend in these values.
In the second row of the periodic table, Be, N, and Ne all have positive (unfavorable) electron affinities, whereas the other second-row elements have negative (favorable) electron affinities. Rationalize why Be, N, and Ne have unfavorable electron affinities.
Order the following atoms from the least negative electron affinity to the most: S, Se.
Order the following atoms from the least negative electron affinity to the most: F, Cl, Br, I.
Order the following atoms from the least negative electron affinity to the most: N, O, F.
Order the following atoms from the least negative electron affinity to the most: Al, Si, P.
The electron affinity for sulfur is more negative than that for oxygen. How do you account for this?
Which has the more negative electron affinity, the oxygen atom or the O- ion? Explain your answer.
Write an equation corresponding to the electron affinity of S-.
Write an equation corresponding to the electron affinity of Fe3+.
Using data from the text, determine the electron affinity of Mg2+. Justify your answer.
The electron affinity of each group 5A element is more positive than that of each corresponding group 4A element. Use the outer electron configurations for these columns to suggest a reason for this observation.
For each of the following pairs of elements:(C and N)     (Ar and Br)pick the atom with the more favorable (more negative) electron affinity.
Which element has the greatest electron affinity (most negative ∆E)?a. Na or Clb. Sr or Ba
Rank these elements according to electron affinity.