Exemplar Problems
Problem 16 : Electronegativity increases from left to right across a period because of increasing effective nuclear charge.
- Electronegativity decreases from top to bottom within a group because of increasing atomic size and shielding effect. .
Solution :
Potassium chloride (KCl) is primarily an ionic compound formed by the transfer of electrons from potassium (K) to chlorine (Cl). Therefore, it exhibits ionic bonding.The statements you provided are accurate explanations for the trends in electronegativity in the periodic table. Let’s break down each statement and provide a brief solution for each:
Statement 1: Electronegativity increases from left to right across a period because of increasing effective nuclear charge.
Solution:
- As you move from left to right across a period (horizontal row) in the periodic table, the number of protons (which determines the positive charge in the nucleus) increases.
- The increase in the number of protons results in a stronger positive charge in the nucleus.
- Electronegativity is the tendency of an atom to attract electrons in a chemical bond. When the effective nuclear charge (positive charge experienced by electrons) increases, the attraction for electrons becomes stronger.
- Therefore, atoms on the right side of a period have a higher electronegativity because they have a greater ability to attract and hold onto electrons due to their increased effective nuclear charge.
Statement 2: Electronegativity decreases from top to bottom within a group because of increasing atomic size and shielding effect.
Solution:
- Within a group (vertical column) in the periodic table, the number of energy levels or electron shells increases as you move down.
- As you move down a group, the atomic size or radius of the atoms increases because there are more electron shells.
- Additionally, the increased number of electron shells results in increased electron-electron repulsions between the electrons in the outermost shell.
- The shielding effect refers to the inner electron shells partially shielding or screening the outer electrons from the full effect of the nucleus’s positive charge.
- Due to the combination of increasing atomic size and the shielding effect, the outermost electrons in lower group elements are farther from the nucleus and experience weaker attractive forces from the nucleus.
- As a result, atoms lower in the same group have lower electronegativity because they are less effective at attracting electrons in chemical bonds compared to their counterparts higher in the group.
These trends in electronegativity are fundamental concepts in chemistry and help explain the behavior of elements in chemical reactions and the formation of chemical bonds.
BETA
