Isoelectronic Species and Ionization Enthalpy
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Questions and Answers

What is the trend of ionization enthalpy across a period?

  • It is uncertain
  • It decreases
  • It remains constant
  • It increases (correct)
  • What is Ionization Enthalpy a measure of?

  • The energy required to remove an electron from an isolated gaseous atom (correct)
  • The energy required to break a chemical bond
  • The energy required to add an electron to an isolated gaseous atom
  • The energy required to form a chemical bond
  • Why does the first ionization enthalpy of boron (Z = 5) decrease compared to that of beryllium (Z = 4)?

  • Due to the decreasing shielding effect
  • Due to the increasing atomic size
  • Due to the increasing nuclear charge
  • Due to the s-electron being attracted more to the nucleus (correct)
  • What is the unit of Ionization Enthalpy?

    <p>kJ mol–1</p> Signup and view all the answers

    What is the effect of shielding on ionization enthalpy down a group?

    <p>Shielding decreases ionization enthalpy</p> Signup and view all the answers

    What is the reaction that represents the first ionization enthalpy for an element X?

    <p>X(g) → X+(g) + e–</p> Signup and view all the answers

    What is the result of the increasing shielding effect down a group?

    <p>The outermost electron is held less tightly</p> Signup and view all the answers

    What is the term for two or more species with the same number of electrons?

    <p>Isoelectronic species</p> Signup and view all the answers

    What is electron gain enthalpy?

    <p>The energy required to add an electron to an atom</p> Signup and view all the answers

    What is the energy required to remove the second most loosely bound electron from an atom?

    <p>Second ionization enthalpy</p> Signup and view all the answers

    What is the effect of nuclear charge on ionization enthalpy across a period?

    <p>It increases ionization enthalpy</p> Signup and view all the answers

    What is the physical state of the atom in the reaction that defines ionization enthalpy?

    <p>Gas</p> Signup and view all the answers

    Why does the ionization enthalpy of Al (Z = 13) decrease compared to that of Mg (Z = 12)?

    <p>Due to the effective shielding of 3p electrons</p> Signup and view all the answers

    What is the general trend of ionization enthalpy down a group?

    <p>It decreases</p> Signup and view all the answers

    Why do O2–, F–, Na+, and Mg2+ have different radii?

    <p>Because they have different nuclear charges</p> Signup and view all the answers

    What is the equation for the reaction that represents the second ionization enthalpy?

    <p>X+(g) → X2+(g) + e–</p> Signup and view all the answers

    What is the general trend of first ionization enthalpy as we go across a period?

    <p>It generally increases</p> Signup and view all the answers

    Why is the second ionization enthalpy higher than the first ionization enthalpy?

    <p>Because it is more difficult to remove an electron from a positively charged ion</p> Signup and view all the answers

    What is the term 'ionization enthalpy' taken as, if not qualified?

    <p>The first ionization enthalpy</p> Signup and view all the answers

    How does the first ionization enthalpy change as we descend a group?

    <p>It decreases</p> Signup and view all the answers

    Why do elements with high reactivity tend to have low ionization enthalpies?

    <p>Because they are more reactive, they are more willing to lose electrons</p> Signup and view all the answers

    Which of the following is NOT a trend in the variation of first ionization enthalpy with atomic number?

    <p>It remains constant across a period</p> Signup and view all the answers

    Why is energy always required to remove electrons from an atom?

    <p>Because energy is required to overcome the attractive forces between the nucleus and electrons</p> Signup and view all the answers

    What is the relationship between ionization enthalpy and atomic radius?

    <p>Ionization enthalpy decreases with increasing atomic radius</p> Signup and view all the answers

    Study Notes

    Isoelectronic Species

    • Isoelectronic species are atoms and ions that contain the same number of electrons
    • Examples of isoelectronic species include O2–, F–, Na+, and Mg2+, which all have 10 electrons
    • Despite having the same number of electrons, isoelectronic species have different radii due to their different nuclear charges

    Ionization Enthalpy

    • Ionization enthalpy is a quantitative measure of an element's tendency to lose an electron
    • It represents the energy required to remove an electron from an isolated gaseous atom in its ground state
    • The unit of ionization enthalpy is kJ mol–1
    • The first ionization enthalpy is the energy required to remove the first electron from an atom
    • The second ionization enthalpy is the energy required to remove the second electron from an atom, and so on
    • Ionization enthalpy is always positive because energy is required to remove electrons from an atom
    • The second ionization enthalpy is higher than the first ionization enthalpy because it is more difficult to remove an electron from a positively charged ion

    Variation of Ionization Enthalpy with Atomic Number

    • The first ionization enthalpies of elements up to atomic number 60 are plotted in Fig. 3.5
    • The graph shows a periodic trend, with maxima at certain points
    • Ionization enthalpy generally increases as you go across a period and decreases as you go down a group
    • This is because the outermost electrons are held more and more tightly as you go across a period, and are increasingly farther from the nucleus as you go down a group

    Electron Gain Enthalpy

    • Electron gain enthalpy is the energy change accompanying the addition of an electron to a neutral gaseous atom to form an anion
    • It provides a measure of the ease with which an atom adds an electron to form an anion
    • The unit of electron gain enthalpy is also kJ mol–1

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    Description

    This quiz covers the concept of isoelectronic species and ionization enthalpy in chemistry. It explains how atoms and ions with the same number of electrons are classified as isoelectronic species and how ionization enthalpy measures the tendency of an element to lose electrons.

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