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How does the electron gain enthalpies...

How does the electron gain enthalpies vary across a period and down a group ?

A

More positive across period and less positive down a group

B

More negative across a period and less negative down a group

C

Less positive across a period and less negative down a group

D

More positive across a period and less negative down a group

Text Solution

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The correct Answer is:
To understand how electron gain enthalpy varies across a period and down a group, we need to analyze the concept of electron gain enthalpy and the trends in the periodic table. ### Step-by-Step Solution: 1. **Definition of Electron Gain Enthalpy**: - Electron gain enthalpy is defined as the amount of energy released when an electron is added to a neutral gaseous atom. It is usually expressed in kJ/mol. 2. **Variation Across a Period**: - As we move from left to right across a period in the periodic table, the electron gain enthalpy generally becomes more negative (i.e., the value increases in magnitude). This means that atoms become more favorable in gaining an electron. - This trend occurs because the effective nuclear charge increases as protons are added to the nucleus while the number of shielding electrons remains relatively constant. As a result, the attraction between the nucleus and the added electron increases, leading to a greater release of energy. 3. **Variation Down a Group**: - When moving down a group in the periodic table, the electron gain enthalpy generally becomes less negative (i.e., the value decreases in magnitude). This indicates that it becomes less favorable for atoms to gain an electron. - This trend can be attributed to the increase in atomic size and the greater distance between the nucleus and the added electron. The increased shielding effect from the inner electron shells also reduces the effective nuclear charge experienced by the added electron, making it less energetically favorable to gain an electron. 4. **Exceptions to the Trend**: - It is important to note that there are exceptions to these trends. For example, noble gases have positive electron gain enthalpies because they have a complete valence shell and do not favor gaining an electron. 5. **Conclusion**: - In summary, electron gain enthalpy becomes more negative across a period due to increasing nuclear charge and less negative down a group due to increased atomic size and shielding effect.
To understand how electron gain enthalpy varies across a period and down a group, we need to analyze the concept of electron gain enthalpy and the trends in the periodic table. ### Step-by-Step Solution: 1. **Definition of Electron Gain Enthalpy**: - Electron gain enthalpy is defined as the amount of energy released when an electron is added to a neutral gaseous atom. It is usually expressed in kJ/mol. 2. **Variation Across a Period**: ...
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Knowledge Check

  • Second electron gain enthalpy:

    A
    is always negative
    B
    is always positive
    C
    can be positive or negative
    D
    is always zero

  • The periodicity is related to the electronic configuration. That is, all chemical and physical properties are a manifestation of the electronic configuration of the elements. The atomic and ionic radii generally decrease in a period from left to right. As a consequence, the ionization enthalpies generally increase and electron gain enthalpies become more negative across a period. In other words, the ionization enthalpy of the exterme left element in a period is the least and teh electron gain enthalpy of the element on the exterme right is the highest negative. This results into high chemical reactivity at the two extermes and the lowest in he centre. Similarly down the group, the increase in atomic and ionic radii result in gradual decrease in ionization enthalpies and a regular decrease (with exception in some third period elements) in electron gain enthalpies in the case of main group elements. The loss and gain of electrons can be co-related with the reducting and oxidising behaviour, and also with metallic and non-metallic character respectively, of the elements. The correct order of the metallic character is:

    A
    `AI gt Mg gt Na gt Si`
    B
    `Na gt Mg lt AI gt Si`
    C
    `Na gt Mg gt AI gt Si`
    D
    `AI gt Mg gt Si gt Na`

  • The periodicity is related to the electronic configuration. That is, all chemical and physical properties are a manifestation of the electronic configuration of the elements. The atomic and ionic radii generally decrease in a period from left to right. As a consequence, the ionization enthalpies generally increase and electron gain enthalpies become more negative across a period. In other words, the ionization enthalpy of the exterme left element in a period is the least and teh electron gain enthalpy of the element on the exterme right is the highest negative. This results into high chemical reactivity at the two extermes and the lowest in he centre. Similarly down the group, the increase in atomic and ionic radii result in gradual decrease in ionization enthalpies and a regular decrease (with exception in some third period elements) in electron gain enthalpies in the case of main group elements. The loss and gain of electrons can be co-related with the reducting and oxidising behaviour, and also with metallic and non-metallic character respectively, of the elements. Which of the following statements is correct?

    A
    ionisation enthalpies of elements decrease along a period and increase along a group in Modern periodic table.
    B
    In the `3^(rd)` period of Modern periodic table, the two most reactive elements are sodium and fluorine.
    C
    Fluorine has the least negative electron gain enthalpy among all halogens.
    D
    Ionisation enthalpy of `Pb` is greater than that of `Sn`.

    • Similar Questions

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    How does valency of an element vary across a period?

    (a) How does the electropositive character of elements change on going down in a group of the periodic table? (b) State how the valency of elements varies (i) in a group and (ii) in a period, of the periodic table.

    The periodicity is related to the electronic configuration. That is, all chemical and physical properties are a manifestation of the electronic configuratio of the elements. The atomic and ionic radii generally decrease in a period from left to right. As a consequence, the ionization enthalpes generally increase and electron gain enthalpies become more negative across a period. In order words, the ionization enthalpy of the extreme left element in a period is the least and the electron gain enthalpy of the element on the extreme right is the highest negative. This results into high chemical reactivity at the two extremes and the lowest in the centre. Similary, down the group, the increase in ionization enthalpies and a regular decrease (with exception in some third period elements) in electron gain enthalpies in the case of main group elements. The loss and gain of electrons can be co-related with the reducing and oxidising behaviour, and also with metallic and non-metallic character respectively of the elements. The correct order of the metallic character is:

    The periodicity is related to the electronic configuration. That is, all chemical and physical properties are a manifestation of the electronic configuratio of the elements. The atomic and ionic radii generally decrease in a period from left to right. As a consequence, the ionization enthalpes generally increase and electron gain enthalpies become more negative across a period. In order words, the ionization enthalpy of the extreme left element in a period is the least and the electron gain enthalpy of the element on the extreme right is the highest negative. This results into high chemical reactivity at the two extremes and the lowest in the centre. Similary, down the group, the increase in ionization enthalpies and a regular decrease (with exception in some third period elements) in electron gain enthalpies in the case of main group elements. The loss and gain of electrons can be co-related with the reducing and oxidising behaviour, and also with metallic and non-metallic character respectively of the elements. The correct order of the non-metallic character is:

    The periodicity is related to the electronic configuration. That is, all chemical and physical properties are a manifestation of the electronic configuratio of the elements. The atomic and ionic radii generally decrease in a period from left to right. As a consequence, the ionization enthalpes generally increase and electron gain enthalpies become more negative across a period. In order words, the ionization enthalpy of the extreme left element in a period is the least and the electron gain enthalpy of the element on the extreme right is the highest negative. This results into high chemical reactivity at the two extremes and the lowest in the centre. Similary, down the group, the increase in ionization enthalpies and a regular decrease (with exception in some third period elements) in electron gain enthalpies in the case of main group elements. The loss and gain of electrons can be co-related with the reducing and oxidising behaviour, and also with metallic and non-metallic character respectively of the elements. Which of the following statements is incorrect?

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