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Questions and Answers
Why is the second ionization enthalpy of an element always higher than its first ionization enthalpy?
Why is the second ionization enthalpy of an element always higher than its first ionization enthalpy?
- The remaining electrons experience increased electron-electron repulsion, stabilizing the ion.
- The atomic radius decreases after the removal of the first electron, increasing the effective nuclear charge.
- The effective nuclear charge experienced by the remaining electrons decreases.
- Removing an electron from a positively charged ion requires more energy to overcome the increased electrostatic attraction. (correct)
Based on the trends of first ionization enthalpies, which of the following elements would likely have the lowest first ionization enthalpy?
Based on the trends of first ionization enthalpies, which of the following elements would likely have the lowest first ionization enthalpy?
- Lithium (Li) (correct)
- Carbon (C)
- Fluorine (F)
- Neon (Ne)
Elements with very stable electron configurations tend to have what relative first ionization enthalpy?
Elements with very stable electron configurations tend to have what relative first ionization enthalpy?
- Their first ionization enthalpy value is near zero.
- Their first ionization enthalpy is highly variable, depending on the number of valence electrons.
- Their first ionization enthalpy is at a maximum. (correct)
- Their first ionization enthalpy is at a minimum.
How does shielding/screening by core electrons affect the effective nuclear charge experienced by valence electrons and, consequently, the ionization enthalpy?
How does shielding/screening by core electrons affect the effective nuclear charge experienced by valence electrons and, consequently, the ionization enthalpy?
Which statement accurately describes the relationship between ionization enthalpy and atomic radius?
Which statement accurately describes the relationship between ionization enthalpy and atomic radius?
Why do alkali metals exhibit low ionization enthalpies?
Why do alkali metals exhibit low ionization enthalpies?
Considering the roles of electron-electron repulsion and attraction of electrons by the nucleus, predict how increasing electron-electron repulsion, while keeping nuclear charge constant, would affect ionization enthalpy.
Considering the roles of electron-electron repulsion and attraction of electrons by the nucleus, predict how increasing electron-electron repulsion, while keeping nuclear charge constant, would affect ionization enthalpy.
In general, as we descend in a group in the periodic table, first ionization enthalpy tends to:
In general, as we descend in a group in the periodic table, first ionization enthalpy tends to:
Boron has a smaller first ionization enthalpy than beryllium. Which of the following contributes to this?
Boron has a smaller first ionization enthalpy than beryllium. Which of the following contributes to this?
Which equation accurately represents the second ionization enthalpy for an element X?
Which equation accurately represents the second ionization enthalpy for an element X?
Flashcards
First Ionization Enthalpy
First Ionization Enthalpy
The energy required to remove the most loosely bound electron from an isolated gaseous atom.
Second Ionization Enthalpy
Second Ionization Enthalpy
Energy needed to remove the second most loosely bound electron.
Why ionization enthalpy is positive?
Why ionization enthalpy is positive?
Energy is needed to overcome attraction between the electron and the nucleus.
Ionization Enthalpy Trends
Ionization Enthalpy Trends
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Periodic Trends of Ionization Enthalpy
Periodic Trends of Ionization Enthalpy
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Factors Affecting Ionization Enthalpy
Factors Affecting Ionization Enthalpy
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Shielding Effect
Shielding Effect
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Study Notes
- First ionization enthalpy for an element X is the enthalpy change (ΔaH) for the reaction: X(g) → X+(g) + e-
- Ionization enthalpy is expressed in kJ mol-1.
- Second ionization enthalpy is the energy needed to remove the second most loosely bound electron: X+(g) → X2+(g) + e-
- Energy is required to remove electrons from an atom, making ionization enthalpies positive.
- The second ionization enthalpy is higher than the first, and so on.
- "Ionization enthalpy," without qualification, refers to the first ionization enthalpy.
Trends in Ionization Enthalpies
- First ionization enthalpies of elements with atomic numbers up to 60 are plotted in Fig 3.5.
- Noble gases, with closed electron shells, show maxima.
- Alkali metals show minima and have low ionization enthalpies.
- High reactivity is correlated with ionization enthalpies
- Ionization enthalpy increases across a period; decreases down a group.
- These trends are demonstrated in Figs 3.6(a) and 3.6(b).
- Fig 3.6(a) shows first ionization enthalpies of elements of the second period as a function of atomic number (Z).
- Li(520), Be(899), B(801), C(1086), N(1402), O(1314), F(1681), Ne(2080).
- Fig 3.6(b) shows ΔaH of alkali metals as a function of Z.
- Li(520), Na(496), K(419), Rb(403), Cs(374).
- Ionization enthalpy and atomic radius are closely related.
- Trends influenced by:
- Attraction of electrons towards the nucleus.
- Repulsion of electrons from each other.
- A valence electron experiences less than the full nuclear charge due to "shielding" or "screening" by core electrons.
- The 2s electron is easier to remove from boron compared to the 2s electron from beryllium.
- Boron's first ionization enthalpy is smaller than beryllium's.
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