Problem 38 - Chemistry: The Central Science

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) True or false: The most easily ionizable elements are the most electronegative.

Step-by-Step Solution

Answer

(a) Electronegativity increases from left to right across a row (period) in the periodic table due to decreasing atomic size and increasing effective nuclear charge experienced by valence electrons. (b) Electronegativity generally decreases going down a column (group) in the periodic table, as atomic size increases and valence electrons are added to higher energy levels further from the nucleus. (c) False. The most easily ionizable elements (i.e., group 1 alkali metals) are not the most electronegative elements, as they have low ionization energies and weak electrostatic attraction between the nucleus and their valence electrons.

Step 1: (a) Electronegativity Trend Across a Row

Electronegativity is the tendency of an atom to attract shared electrons in a chemical bond. As we move from left to right across a row (period) in the periodic table, the electronegativity of the elements increases. This is due to the decrease in atomic size and an increase in the effective nuclear charge experienced by the valence electrons, which increases the electrostatic attraction between the nucleus and the electrons.

Step 2: (b) Electronegativity Trend Down a Column

Going down a column (group) in the periodic table, the electronegativity of the elements generally decreases. This is because the atomic size increases, and electrons are being added to higher energy levels which are further from the nucleus. The increasing distance between the nucleus and the valence electrons reduces the attractive force between them, resulting in lower electronegativity values.

Step 3: (c) Ionization and Electronegativity Statement

"The most easily ionizable elements are the most electronegative." This statement is false. The most easily ionizable elements are found in group 1 (alkali metals), as they have low ionization energies due to their large atomic size and weak electrostatic attraction between the nucleus and their single valence electron. On the other hand, the electronegative elements such as fluorine are not easily ionizable, as they have high electronegativity values and strong attraction between their nucleus and valence electrons. Therefore, the statement is false.