Answer true or false.
(a) The name of a binary ionic compound consists of the name of the positive ion followed by the name of the negative ion.
(b) In naming binary ionic compounds, it is necessary to state the number of each ion present in the compound.
(c) The formula of aluminum oxide is Al2 O3 .
(d) Both copper(II) oxide and cupric oxide are acceptable names for CuO.
(e) The systematic name for Fe2 O3 is iron(II) oxide.
(f) The systematic name for FeCO3 is iron carbonate.
(g) The systematic name for NaH2PO4 is sodium di- hydrogen phosphate.
(h) The systematic name for K2HPO4 is dipotassium hydrogen phosphate.
(i) The systematic name for Na2O is sodium oxide.
(j) The systematic name for PCl3 is potassium chloride.
(k) The formula of ammonium carbonate is NH4CO3.
39.
(a) A covalent bond is formed between two atoms whose difference in electronegativity is less than 1.9.
(b) If the difference in electronegativity between two atoms is zero (they have identical electronegativ- ities), then the two atoms will not form a covalent bond.
(c) A covalent bond formed by sharing two electrons is called a double bond.
(d) In the hydrogen molecule (H2), the shared pair of electrons completes the valence shell of each hydrogen.
(e) In the molecule CH4 , each hydrogen has an electron configuration like that of helium and carbon has an electron configuration like that of neon.
(f) In a polar covalent bond, the more electronegative atom has a partial negative charge (ÂÂ2) and the less electronegative atom has a partial positive charge (ÂÂ1).
(g) These bonds are arranged in order of increasing polarity CiH , NiH , OiH.
(h) These bonds are arranged in order of increasing polarity HiF , HiCl , HiBr. (
i) A polar bond has a dipole with the negative end located at the more electronegative atom.
(j) In a single bond, two atoms share one pair of electrons; in a double bond, they share two pairs of electrons; and in a triple bond, they share three pairs of electrons.
(k) The Lewis structure for ethane, C2H6, must show eight valence electrons.
(l) The Lewis structure for formaldehyde, CH2 O, must show 12 valence electrons.
(m) The Lewis structure for the ammonium ion, NH4 1, must show nine valence electrons.
(n) Atoms of third-period elements can hold more than eight electrons in their valence shells.
The Correct Answer and Explanation is :
Here are the true or false answers, followed by a 300-word explanation:
Answers:
Binary Ionic Compounds:
(a) True
(b) False – The number of each ion is not explicitly stated in the name, as ionic compounds naturally balance charges.
(c) True – The correct formula for aluminum oxide is Al₂O₃.
(d) True – Copper(II) oxide and cupric oxide both correctly name CuO.
(e) False – The systematic name for Fe₂O₃ is iron(III) oxide, not iron(II) oxide.
(f) True – The correct name for FeCO₃ is iron(II) carbonate (or simply iron carbonate).
(g) True – NaH₂PO₄ is named sodium dihydrogen phosphate.
(h) True – K₂HPO₄ is named dipotassium hydrogen phosphate.
(i) True – Na₂O is named sodium oxide.
(j) False – PCl₃ is named phosphorus trichloride, not potassium chloride.
(k) False – The correct formula for ammonium carbonate is (NH₄)₂CO₃, not NH₄CO₃.
Covalent Bonding:
(a) True – A covalent bond forms when the difference in electronegativity is less than 1.9.
(b) False – Even if the difference is zero, the atoms can still form a nonpolar covalent bond.
(c) False – A covalent bond sharing two electrons is a single bond, not a double bond.
(d) True – In H₂, both hydrogen atoms achieve a full valence shell by sharing electrons.
(e) True – In CH₄, hydrogen attains the helium configuration, and carbon attains the neon configuration.
(f) True – In a polar covalent bond, the more electronegative atom gets a partial negative charge, and the less electronegative atom gets a partial positive charge.
(g) True – Polarity increases as C–H < N–H < O–H due to electronegativity differences.
(h) True – Polarity increases as H–I < H–Br < H–Cl < H–F.
(i) True – A polar bond has a dipole moment where the negative end is at the more electronegative atom.
(j) True – Single bond = one pair, double bond = two pairs, triple bond = three pairs of electrons.
(k) False – C₂H₆ must show 14 valence electrons (not 8).
(l) True – CH₂O must show 12 valence electrons (4 from carbon, 6 from oxygen, 2 from hydrogen).
(m) False – The ammonium ion (NH₄⁺) has 8 valence electrons, not 9, due to the positive charge.
(n) True – Third-period elements like phosphorus and sulfur can have expanded octets (more than 8 electrons).
Explanation:
Ionic and covalent compounds follow distinct naming conventions and bonding rules. Binary ionic compounds consist of a metal cation and a nonmetal anion, with the cation name first and the anion name second (e.g., NaCl = sodium chloride). The charges must balance, but numbers of ions are not explicitly stated unless using a Roman numeral system for transition metals (e.g., Fe₂O₃ = iron(III) oxide).
Covalent bonds form when atoms share electrons. A polar covalent bond occurs when electronegativity differences create a dipole (e.g., H–F). A nonpolar bond occurs when atoms have similar electronegativities, like O₂ or N₂.
The Lewis structures of molecules help visualize bonding and valence electrons. Some molecules follow the octet rule (8 valence electrons), but third-period elements (like sulfur or phosphorus) can have expanded octets, holding more than 8 electrons.
Understanding bonding, naming conventions, and valence electron arrangements is essential in chemistry to predict molecular properties, reactivity, and stability.