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.
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.
What are the observed periodic trends in electron affinity?
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?
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
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.
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 of the following atoms has the  highest (most negative) electron affinity?a) Nab) Clc) Brd) Se) As
Would a neutral K atom or a K+ ion have a more negative value of electron affinity?
The electron affinity value expected for the reactionKr(g) + e → Kr -(g)  would bea) a large negative numberb) a small negative numberc) zerod) greater than that for Ar(g)e) meaningless because Kr already has a stable noble gas configuration
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.
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
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.
The following table gives the electron affinities, in kJ/mol, for the group 1B and group 2B metals.The electron affinities, in kJ/mol, for the group 1B and group 2B metals are as follows:Why are the electron affinities of the group 2B elements greater than zero?
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-.
Choose the element with the more negative (more exothermic) electron affinity from each pair:a. Mg or Sb. K or Csc. Si or Pd. Ga or Br
For which element is the gaining of an electron most exothermic?a) Lib) Nc) Fd) B
Group 4A elements have much more negative electron affinities than their neighbors in groups 3A and 5A (see the figure).Which of the following statements best explains this observation?(i) The group 4A elements have much higher first ionization energies than their neighbors in groups 3A and 5A.(ii) The addition of an electron to a group 4A element leads to a half-filled np3 outer electron configuration.(iii) The group 4A elements have unusually large atomic radii.(iv) The group 4A elements are easier to vaporize than are the group 3A and 5A elements.
Which of the following chemical equations is connected to the definitions of the electron affinity of oxygen?(i) O(g) + e– → O–(g)(ii) O(g) → O+(g) + e–(iii) O(g) + 2 e– → O2–(g)(iv) O(g) → O2+(g) + 2 e–(v) O+(g) → O2+(g) + e–
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.
In general, as you go across a period in the periodic table from left to right:(1) the atomic radius __________;(2) the electron affinity becomes __________ negative; and(3) the first ionization energy __________.A) decreases, decreasingly, increasesB) increases, increasingly, decreasesC) increases, increasingly, increasesD) decreases, increasingly, increasesE) decreases, increasingly, decreases
Which element has the highest (most negative) electron affinity?a. Xeb. Sc. Csd. Bae. Cu
Of the following elements, __________ has the most negative electron affinity.A) NaB) LiC) BeD) NE) F
Of the following elements, __________ has the most negative electron affinity.A) SB) ClC) SeD) BrE) I
Of the following elements, __________ has the most negative electron affinity.A) PB) AlC) SiD) ClE) B
Which element has the most negative electron affinity out of the following choices?a. Ib. Brc. Cld. Pe. Na
Which atom in each set has the most exothermic electron affinity?i) N, O, Neii) Al, Si, Cla. i) Ne ii) Clb. i) N ii) Clc. i) O ii) Cld. i) Ne ii) Sie. i) O ii) Al
Which reaction below represents the electron affinity of Be?a. Be(g) → Be+(g) + e-b. Be(g) + e- → Be-(g) c. Be+(g) → Be(g) + e-d. Be(g) + e- → Be+(g)e. Be+(g) + e- → Be(g)
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–
Which halogen has the lowest electron affinity?
Rank these elements according to electron affinity. 
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
Choose the element with the more negative (more exothermic) electron affinity from each of the following pairs.Li or F
Write an equation corresponding to the electron affinity of Fe3+.
Which element has the highest first electron affinity?a. Ob. Mgc. Nad. Ne
Which element has the greatest electron affinity (most negative ∆E)?a. Na or Clb. Sr or Ba
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
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
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
Rank these elements according to electron affinity.