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Define electronegativity - Leaving Cert Chemistry - Question a - 2013
Question a
Define electronegativity. Explain why electronegativity values (i) increase across a period, (ii) decrease down a group, in the periodic table. Use electronegativi... show full transcript
Worked Solution & Example Answer:Define electronegativity - Leaving Cert Chemistry - Question a - 2013
Step 1
Step 2
Explain why electronegativity values (i) increase across a period.
Answer
Electronegativity values increase across a period due to the increase in nuclear charge. As protons are added to the nucleus, the positive charge increases, which enhances the attraction between the nucleus and the shared pair of electrons. Additionally, the atomic radius decreases due to increased effective nuclear charge, bringing the bonding electrons closer to the nucleus.
Step 3
Explain why electronegativity values (ii) decrease down a group.
Answer
Electronegativity values decrease down a group primarily because of the increase in atomic radius. As you move down the group, additional electron shells are added, increasing the distance between the nucleus and the bonding electrons. Moreover, the effect of electron shielding increases, wherein the inner-shell electrons repel the valence electrons, making it harder for the nucleus to attract these shared electrons.
Step 4
Use electronegativity values to predict the bonding in hydrogen chloride (HCl).
Answer
Hydrogen chloride (HCl) is predicted to have polar covalent bonding. This is due to the difference in electronegativity between hydrogen and chlorine, where chlorine has a significantly higher electronegativity, causing a partial negative charge at the chlorine end.
Step 5
Use electronegativity values to predict the bonding in sodium chloride (NaCl).
Answer
Sodium chloride (NaCl) is predicted to have ionic bonding. Sodium has a much lower electronegativity compared to chlorine. Sodium donates its electron to chlorine, resulting in the formation of Na+ and Cl- ions, leading to an ionic compound.
Step 6
Use electronegativity values to predict the bonding in hydrogen (H2).
Answer
Hydrogen (H2) is predicted to have purely covalent bonding. Both atoms in H2 have the same electronegativity, which means the shared pair of electrons is equally attracted to both nuclei, resulting in a nonpolar covalent bond.