Question

(a) What is the trend in electronegativity going from left to right in a row of the periodic table? (b) How do electronegativity values generally vary going down a column in the periodic table? (c) How do periodic trends in electronegativity relate to those for ionization energy and electron affinity?

Short answer

Going from left to right in a row of the periodic table, electronegativity increases due to an increased positive nuclear charge. In contrast, electronegativity tends to decrease going down a column because of the increasing distance between the nucleus and outermost electrons. Similar trends are observed for ionization energy. Electron affinity also increases from left to right in a row, while its trend going down a column is less clear-cut but generally decreases with some exceptions. All three properties are related to an atom's ability to attract, lose, or gain electrons based on atomic size, nuclear charge, and electron shell distances.

Step-by-step solution

Electronegativity definition

Electronegativity is a measure of an atom's ability to attract an electron pair in a covalent bond. The greater the electronegativity value of the atom, the stronger the pull for the shared electrons.

Trend in electronegativity from left to right in a row

Going from left to right in a row of the periodic table, the electronegativity increases. This is because, as we move from left to right, the number of protons increases, leading to a stronger positive charge in the nucleus. This increased positive charge attracts the shared electrons more, hence making the electronegativity increase.

Trend in electronegativity going down a column

Going down a column in the periodic table, the electronegativity generally decreases. This is because, as we go down a group, the number of electron shells increases, resulting in a greater distance between the outermost electrons and the nucleus. As a result, the force attracting the electron pair in a covalent bond is weaker, leading to a decrease in electronegativity.

Ionization energy and electron affinity definitions

Ionization energy is the energy required to remove an electron from an atom, while electron affinity is the energy released when an electron is added to an atom.

Relation between electronegativity, ionization energy, and electron affinity trends

As mentioned earlier, electronegativity increases from left to right in a row and decreases going down a column in the periodic table. Similarly, ionization energy also increases from left to right and decreases going down a column due to the same reasons discussed earlier. Electron affinity, on the other hand, shows a similar trend of increasing from left to right in a row. However, the trend going down a column may not be as clear-cut as the other properties. For electron affinity, in general, the trend is to decrease from top to bottom, although there may be some exceptions. In general, all three properties are related to the ability of an atom to attract, lose, or gain electrons based on its size, nuclear charge, and the distance between the nucleus and outermost electrons.