Valence Electrons & Ion Formation
How many valence electrons does phosphorus have?
5
What is the main difference between ionic and covalent bonding?
Ionic involves electron transfer; covalent involves electron sharing.
How many valence electrons does oxygen have in its Lewis dot structure?
6
What is the molecular geometry of CH₄?
Tetrahedral
Name Na₂O.
Sodium oxide
What ion does aluminum typically form, and why?
Al³⁺; it loses 3 valence electrons.
Classify MgCl₂ and CO₂ as ionic or covalent.
MgCl₂: ionic; CO₂: covalent.
Draw the Lewis structure for H₂O. How many lone pairs are on oxygen?
Two single O–H bonds and 2 lone pairs on O.
What is the molecular geometry of H₂O?
Bent
Write the formula for dinitrogen tetroxide.
N₂O₄
Which has a higher first ionization energy, sodium or magnesium? Explain.
Magnesium; its valence electrons experience stronger effective nuclear attraction.
Explain why magnesium and chlorine form MgCl₂ rather than MgCl.
Mg loses 2 electrons, while each Cl gains 1. Two Cl⁻ ions are needed to balance Mg²⁺.
Draw the Lewis structure for CO₂. How many double bonds are present?
O=C=O; two double bonds.
NH₃ has three bonding domains and one lone pair. What is its molecular geometry?
Trigonal pyramidal
Name FeCl₃. Explain the Roman numeral.
Iron(III) chloride; iron has a +3 charge.
An element has 7 valence electrons. Predict its ionic charge and explain.
−1; it gains one electron to achieve an octet.
Determine the formula formed between Al³⁺ and SO₄²⁻. Explain how the charges balance.
Al₂(SO₄)₃; two Al³⁺ ions give +6, and three sulfate ions give −6.
Draw the Lewis structure for HCN. Identify the single and triple bonds.
H–C≡N; one single bond and one triple bond.
Explain why CO₂ is linear while H₂O is bent.
CO₂ has two bonding domains and no lone pairs on carbon. H₂O has two bonding domains and two lone pairs on oxygen.
Write the formulas for calcium nitrate and copper(II) sulfate.
Ca(NO₃)₂ and CuSO₄
A student claims potassium has a higher ionization energy than lithium because it has more protons. Evaluate this claim.
Incorrect. Potassium has greater shielding and a larger atomic radius, making its outer electron easier to remove.
A student writes Ca₃N₂ as Ca₂N₃. Explain the mistake and justify the correct formula.
Ca²⁺ and N³⁻ must combine in a 3:2 ratio to produce a neutral compound: Ca₃N₂.
A student draws BF₃ with a lone pair on boron. Explain the error and draw the correct structure.
Boron forms three single bonds with fluorine and has no lone pairs. It is stable with six electrons in this structure.
Identify the molecular geometry, bonding domains, and nonbonding domains of SF₆ and PF₅.
SF₆: octahedral, 6 bonding, 0 nonbonding. PF₅: trigonal bipyramidal, 5 bonding, 0 nonbonding.
A student names Cu₂O copper(II) oxide. Explain why this is incorrect and provide the correct name.
Copper(I) oxide. Oxygen is −2, so each copper must be +1.