Worksheet: Ionization Energy and Electron Affinity

In this worksheet, we will practice comparing the ionization energies and electron affinities of the elements, explaining trends across the periodic table.

Q1:

An electron is removed from a gaseous atom. For which of the five elements Sn, Si, Sb, O, and Te is this process most endothermic?

  • ASn
  • BTe
  • CO
  • DSi
  • ESb

Q2:

Which main group element has the lowest second ionization energy?

  • ABe
  • BRa
  • CO
  • DFr
  • EF

Q3:

Which of the following elements has the lowest first ionization energy?

  • ASr
  • BO
  • CPo
  • DPb
  • EBa

Q4:

In which of the following sequences are the ionization energies arranged in order of increasing size? Note that IEX() is the 𝑛th ionization energy of element X.

  • AIE1(Tl) < IE2(Na) < IE1(Al) < IE3(Al)
  • BIE1(Tl) < IE1(Al) < IE3(Al) < IE2(Na)
  • CIE2(Na) < IE3(Al) < IE1(Tl) < IE1(Al)
  • DIE3(Al) < IE1(Al) < IE1(Tl) < IE2(Na)
  • EIE1(Al) < IE1(Tl) < IE2(Na) < IE3(Al)

Q5:

Which of the following elements has the largest first ionization energy?

  • AO
  • BMg
  • CTe
  • DB
  • EBa

Q6:

Which of the following elements has the smallest first ionization energy?

  • ANa
  • BSr
  • CBr
  • DRb
  • EP

Q7:

Rank the following atoms in order of increasing first ionization energy: Ca, S, Se, Ge.

  • AS<Ca<Ge<Se
  • BGe<Ca<Se<S
  • CS<Se<Ca<Ge
  • DCa<Ge<Se<S
  • ECa<Ge<S<Se

Q8:

An electron is added to a gaseous ion with a charge of +1. For which of the five elements Ga, Br, I, K, and Rb is this process most exothermic?

  • AI
  • BBr
  • CK
  • DGa
  • ERb

Q9:

Which of the following elements has the largest first ionization energy?

  • AB
  • BBa
  • CO
  • DTe
  • EMg

Q10:

Which of the following elements has the smallest first ionization energy?

  • AP
  • BNa
  • CSr
  • DBr
  • ERb

Q11:

Rank the following atoms in order of increasing first ionization energy: F, Li, N, Rb.

  • ALi<Rb<N<F
  • BF<N<Li<Rb
  • CRb<Li<N<F
  • DRb<Li<F<N
  • EN<F<Rb<Li

Q12:

Rank the following atoms in order of increasing first ionization energy: Ca, S, Se, Ge.

  • AS<Se<Ca<Ge
  • BS<Ca<Ge<Se
  • CCa<Ge<S<Se
  • DCa<Ge<Se<S
  • EGe<Ca<Se<S

Q13:

Which of the following elements has the greatest first electron affinity?

  • AS
  • BSe
  • CI
  • DBr
  • ECl

Q14:

Why is the electron affinity of F less than that of Cl?

  • AThere is a larger effective nuclear charge acting on the valence electrons of the Cl atom.
  • BThe Cl atom has a larger nuclear charge.
  • CThe F atom has a higher electron density, so it repels the added electron more strongly.
  • DThe Cl atom contains filled d orbitals which shield the valence p subshell less effectively.
  • EThe Cl atom has a lower first ionization energy.

Q15:

Why is the first electron affinity of O less than that of F?

  • AThere is a smaller effective nuclear charge acting on the valence electrons of the O atom.
  • BThe O atom has a higher electron density so it repels the added electron more strongly.
  • CThe pairing energy is greater when an electron is added to the O atom.
  • DElectrons in the p subshell of the O atom are more effectively shielded by core shell electrons.
  • EAdding an electron to the F atom produces a full electron shell.

Q16:

Why is the first ionization energy of F greater than that of Cl?

  • AThere is a larger effective nuclear charge acting on the valence electrons of the F atom.
  • BPairing energy is reduced by a greater amount when an electron is removed from the F atom.
  • CThe electron removed from the F atom has a smaller principal quantum number.
  • DElectrons in the p subshell of the F atom are more effectively shielded by core shell electrons.
  • EElectrons in the p subshell of the F atom are more effectively shielded by valence s electrons.

Q17:

Why is the first ionization energy of Ga slightly greater than that of Al?

  • AThe electron removed from the Ga atom has a smaller principal quantum number.
  • BFor every proton in the nucleus, the valence p electrons in the Ga atom are shielded by fewer electrons in lower energy subshells.
  • CThe Ga atom contains filled d orbitals that shield the valence p subshell less effectively.
  • DPairing energy is reduced by a greater amount when an electron is removed from the Al atom.
  • EThe average radial distance of valence electrons from the nucleus is smaller in the Ga atom.

Q18:

Why is the first ionization energy of Be greater than that of Li?

  • ABecause removal of an electron from the Li atom is assisted by a decrease in pairing energy
  • BBecause the electron removed from the Be atom has a smaller principal quantum number
  • CBecause removing an electron from the Li atom produces an empty electron shell
  • DBecause electrons in the p subshell of the Be atom are more effectively shielded by core shell electrons
  • EBecause there is a larger effective nuclear charge acting on the valence electrons of the Be atom

Q19:

Why does Mg have a higher first ionization energy than Al?

  • AThe 3p subshell of the Al atom is shielded by the 3s subshell.
  • BIt is more difficult to remove an electron from a filled subshell.
  • CPair repulsion in the 3p subshell makes it easier to remove an electron from the Al atom.
  • DThe atomic radius of Al is larger.
  • EThe Al atom has more valence electrons to remove.

Q20:

Why is the second ionization energy of Na greater than that of Mg?

  • ARemoving an electron from the Mg+ ion produces an empty electron shell.
  • BRemoving an electron from the Mg+ ion is assisted by a decrease in pairing energy.
  • CThe electron removed from the Mg+ ion has a larger principal quantum number.
  • DThe electron removed from the Mg+ ion has a smaller azimuthal quantum number.
  • ERemoving an electron from the Mg+ ion produces an ion with a larger radius.

Q21:

Why does S have lower first ionization energy than P?

  • AThe atomic radius of S is larger.
  • BIt is more difficult to remove an electron from a subshell if doing so results in an unfilled orbital.
  • CElectrons in the full 3p orbital of the S atom experience pair repulsion.
  • DThe 3p electrons of the S atom are more strongly shielded by the 3s subshell.
  • EThe S atom has a higher maximum oxidation state.

Q22:

Rank the elements from N to Ne in order of decreasing first ionization energy.

  • ANe>F>O>N
  • BF>O>N>Ne
  • CN>O>Ne>F
  • DNe>F>N>O
  • EO>N>F>Ne

Q23:

Which of the following elements has the highest first ionization energy?

  • AB
  • BN
  • CBe
  • DO
  • EC

Q24:

Which of the following quantities can be increased to raise the ionization energy?

  • AElectron shielding
  • BAtomic radius
  • CPrincipal quantum number of the valence shell
  • DEffective nuclear charge
  • EPairing energy

Q25:

Which quantity is equal in magnitude to the change in energy for the reaction shown? X()+eX()2++gg

  • ASecond electron affinity
  • BFirst ionization energy
  • CThird ionization energy
  • DSecond ionization energy
  • EFirst electron affinity

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