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Zorluk: ZorIonic (Electrovalent) Bonding and Properties of Ionic Compounds

Consider four main group elements PP, QQ, RR, and SS with atomic numbers 1111, 1212, 1616, and 1717 respectively. Which combination of these elements forms an electrovalent compound with the highest melting point?

  1. The combination of QQ and SS, because the +2+2 and −2-2 ionic charges maximize the electrostatic lattice attraction.Cevap
  2. B
    The combination of PP and RR, because single electron transfer minimizes interionic repulsion within the crystal lattice.
  3. C
    The combination of QQ and RR, because a 1:21:2 stoichiometric ratio produces the highest crystal packing density.
  4. D
    The combination of PP and SS, because two P+P^+ cations double the total electrostatic pull on a single S2−S^{2-} anion.

Cevap

The combination of element Q (atomic number 12) and element S (atomic number 16) forms QS, which has the highest melting point due to the +2 and -2 ionic charges maximizing electrostatic lattice attraction.
Element Q (atomic number 12) has electronic configuration 2,8,2 and loses two electrons to form Q2+. Element S (atomic number 16) has electronic configuration 2,8,6 and gains two electrons to form S2-. The compound formed between Q and S (QS) consists of divalent ions. By Coulomb's Law, lattice energy is proportional to the product of ionic charges (|q1 * q2|). The charge product for QS is 4, which is double that of QR2 or P2S (charge product 2) and four times that of PR (charge product 1). Consequently, QS possesses the highest lattice energy and highest melting point.

Adım Adım Çözüm

1
Determine the identity and valency of each element from its atomic number
PP (Z=11Z=11, Sodium) forms P+P^+ cations; QQ (Z=12Z=12, Magnesium) forms Q2+Q^{2+} cations; SS (Z=16Z=16, Sulfur) forms S2−S^{2-} anions; RR (Z=17Z=17, Chlorine) forms R−R^- anions.
Electronic configurations determine the number of valence electrons lost or gained to achieve stable octet structures.
2
Write the chemical formulas for the electrovalent compounds formed by valid metal-nonmetal pairs
Possible ionic compounds are PRPR (P+R−P^+ R^-), P2SP_2S ((P+)2S2−(P^+)_2 S^{2-}), QR2QR_2 (Q2+(R−)2Q^{2+} (R^-)_2), and QSQS (Q2+S2−Q^{2+} S^{2-}).
Electrovalent compounds form when metals transfer electrons to non-metals to achieve electrical neutrality.
3
Compare the electrostatic lattice energies of the resulting crystal lattices
Lattice energy is directly proportional to the product of ionic charges (Elattice∝∣q1q2∣E_{\text{lattice}} \propto |q_1 q_2|). For QSQS, ∣q1q2∣=∣(+2)(−2)∣=4|q_1 q_2| = |(+2)(-2)| = 4. For QR2QR_2 and P2SP_2S, ∣q1q2∣=2|q_1 q_2| = 2. For PRPR, ∣q1q2∣=1|q_1 q_2| = 1.
According to Coulomb's Law, higher ionic charges create substantially stronger electrostatic forces of attraction between ions in the solid lattice.
4
Relate lattice energy to the physical property of melting point
Higher lattice energy requires significantly more thermal energy to break the ionic bonds, making QSQS the compound with the highest melting point.
The melting point of an electrovalent compound increases as the strength of the lattice attraction increases.

Anahtar Kavram

Lattice energy dependence on ionic charge magnitude (Coulomb's Law in ionic crystals)
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Konular

Ionic (Electrovalent) Bonding and Properties of Ionic Compounds

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