Bonding, Formulas & Molecular Structure — Chapter Practice, Grade 11

Build names, formulas, Lewis structures, and structure-property explanations.

Problem 1

Which type of element usually forms a cation by losing electrons?
  1. a halogen
  2. a metal
  3. a nonmetal
  4. a noble gas
Answer and explanation

a metal

Metals hold their few valence electrons loosely and lose them to become positive cations.

Problem 2

When a chlorine atom gains one electron, the ion it forms is called…
  1. a molecule
  2. a cation
  3. an anion
  4. a proton
Answer and explanation

an anion

Gaining an electron gives the atom a negative charge, making it an anion (Cl⁻).

Problem 3

Aluminum forms Al³⁺ and oxygen forms O²⁻. In the neutral compound aluminum oxide, how many oxide ions combine with every 2 aluminum ions?
Answer and explanation

3

Two Al³⁺ give +6, so you need three O²⁻ (−2 each) to reach −6 and balance the charge: Al₂O₃.

Problem 4

Why does solid table salt (NaCl) NOT conduct electricity, while molten NaCl does?
  1. Solid salt contains no charged particles
  2. Electrons flow easily through solid salt
  3. Melting adds extra electrons to the salt
  4. The ions are locked in place in the solid lattice but are free to move when molten
Answer and explanation

The ions are locked in place in the solid lattice but are free to move when molten

Conduction needs mobile charges; the lattice freezes the ions in place, but melting frees them to move and carry current.

Problem 5

Explain, in terms of electrons, why a sodium atom and a chlorine atom form an ionic bond.
Answer and explanation

Sodium has 1 valence electron and chlorine has 7. Sodium transfers its single electron to chlorine, so both reach a full outer shell. Sodium becomes Na⁺ and chlorine becomes Cl⁻, and the opposite charges attract to form the ionic bond.

Problem 6

An ion with a 3+ charge combines with an ion with a 2− charge. Using the criss-cross rule, how many ions in total (cations plus anions) are in one formula unit of the compound?
Answer and explanation

5

Balancing +3 and −2 needs 2 cations (+6) and 3 anions (−6), so one formula unit has 2 + 3 = 5 ions.

Problem 7

Find the neutral formula from Ca²⁺ and Cl⁻. Show the reasoning, not just the conclusion.
Hints

Ionic formulas give ratios in a lattice, not necessarily individual molecules.

Answer and explanation

CaCl₂, because +2 balances two −1 charges.

Problem 8

Why can molten sodium chloride conduct while its solid usually cannot?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Mobile ions carry charge in the melt; ions are constrained in the solid lattice under ordinary conditions.

Problem 9

Conductivity depends on movable charge, not merely charged speciesConductivity depends on movable charge, not merely charged speciesSolidMolten / dissolvedCharge carriers must be mobile for sustained conduction.+−+−+−+−−+
Original qualitative mobility comparison; arrows indicate possible ion motion, not a specific voltage polarity or measured conductivity.
Interpret the supplied visual. Why can a salt solution conduct even though an intact salt crystal usually conducts poorly?
Answer and explanation

Dissolved ions can move through the solution; lattice-bound ions in the ordinary solid are far less mobile.

A solid ionic crystal contains charged ions, but their positions are constrained by the lattice and they do not provide ordinary bulk ionic conduction. Melting or dissolving can make ions mobile, allowing them to carry current under suitable conditions. This does not mean every ionic compound dissolves readily or that solid conductivity is mathematically zero under all conditions. Identify phase, temperature, concentration and the relevant charge carrier before interpreting a conductivity comparison.

Dissolved ions can move through the solution; lattice-bound ions in the ordinary solid are far less mobile.

Response criteria

  • Interpret labels, structures, axes, units and directions correctly.
  • Explain the chemistry relationship or mechanism.
  • Respect stated assumptions and distinguish observation from inference.

Problem 10

Al³⁺ combines with O²⁻. Find the simplest neutral formula and explain why it is not a five-ion molecule drawing for the solid.
Answer and explanation

The least common charge magnitude is 6: two Al³⁺ and three O²⁻ give +6−6=0, so Al₂O₃. The formula states a stoichiometric ratio in an extended solid, not a claim of isolated five-ion molecules.

The least common charge magnitude is 6: two Al³⁺ and three O²⁻ give +6−6=0, so Al₂O₃. The formula states a stoichiometric ratio in an extended solid, not a claim of isolated five-ion molecules.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the chemical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 11

A covalent bond forms when two atoms…
  1. share electrons
  2. lose electrons
  3. gain protons
  4. transfer electrons
Answer and explanation

share electrons

Covalent bonding is the sharing of one or more pairs of electrons between atoms.

Problem 12

Covalent bonds usually form between…
  1. two metals
  2. a metal and a nonmetal
  3. two nonmetals
  4. two noble gases
Answer and explanation

two nonmetals

Two nonmetals both attract electrons strongly, so they share rather than transfer, forming covalent bonds.

Problem 13

How many electrons are shared in a single covalent bond?
Answer and explanation

2

A single bond is one shared pair, and a pair is 2 electrons.

Problem 14

A nitrogen molecule (N₂) contains a triple bond. How many electrons are shared between the two nitrogen atoms?
Answer and explanation

6

A triple bond is 3 shared pairs, and 3 pairs × 2 electrons = 6 electrons.

Problem 15

Explain why molecular compounds like water tend to have much lower melting points than ionic compounds like salt.
Answer and explanation

In a molecular compound the covalent bonds inside each molecule are strong, but the attractions between separate molecules are weak, so little energy is needed to pull the molecules apart. In an ionic compound every ion is locked to its neighbors by strong electrostatic forces throughout the lattice, so far more energy — a higher temperature — is needed to break it apart.

Problem 16

In the Lewis structure of carbon dioxide (O=C=O), how many lone pairs are on each oxygen atom?
  1. 1
  2. 2
  3. 3
  4. 0
Answer and explanation

2

Each oxygen shares 2 pairs in its double bond and keeps 2 lone pairs of its own, completing its octet.

Problem 17

How many shared electrons are represented by a triple bond? Show the reasoning, not just the conclusion.
Hints

A shared pair is not ownership transferred permanently to only one atom.

Answer and explanation

Six electrons in three shared pairs in the simple bond model.

Problem 18

Why can a covalent molecule be polar even though it is electrically neutral?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Partial charge separation can create a net molecular dipole without net charge.

Problem 19

Bond-order comparisons need a matched chemical contextBond-order comparisons need a matched chemical contextSelected C–C bondRelative lengthBonding modelSingleLongerOne shared pairDoubleIntermediateTwo shared pairsTripleShorterThree shared pairsCompare compatible species; energy is not simply pair-count × constant.Resonance and chemical context can change the comparison.
Original qualitative matched C–C comparison; no universal bond-length or bond-energy dataset is asserted.
Interpret the supplied visual. Does a C=C double bond have exactly twice the dissociation energy of every C–C single bond?
Answer and explanation

No. Bond order supports a qualitative comparison for suitable species, but measured energy depends on the full bonding environment and defined process.

Bond order summarizes bonding in a model: a Lewis single, double or triple line commonly represents one, two or three shared pairs. For comparable atom pairs, higher bond order often corresponds to shorter, stronger bonds, but bond energies are not exact integer multiples and depend on the surrounding molecule. Bond dissociation energy concerns a specified bond-breaking process. Delocalized structures can have intermediate effective orders, so a selected Lewis drawing should not be treated as a direct ruler or calorimeter.

No. Bond order supports a qualitative comparison for suitable species, but measured energy depends on the full bonding environment and defined process.

Response criteria

  • Interpret labels, structures, axes, units and directions correctly.
  • Explain the chemistry relationship or mechanism.
  • Respect stated assumptions and distinguish observation from inference.

Problem 20

Compare CO₂ and H₂O: both have polar bonds. Explain why bond polarity alone cannot establish that both molecules have a net dipole.
Answer and explanation

CO₂ is linear with equal opposing bond contributions that cancel in the ideal symmetric molecule. H₂O is bent, so its bond dipoles do not cancel. Geometry and the full charge distribution matter.

CO₂ is linear with equal opposing bond contributions that cancel in the ideal symmetric molecule. H₂O is bent, so its bond dipoles do not cancel. Geometry and the full charge distribution matter.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the chemical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 21

In the electron-sea model, metal atoms are best described as…
  1. separate molecules sharing electron pairs
  2. neutral atoms locked rigidly in place
  3. positive ions surrounded by mobile, delocalized electrons
  4. negative ions in a fixed lattice
Answer and explanation

positive ions surrounded by mobile, delocalized electrons

Metals form positive ions that sit in a shared sea of freely moving delocalized electrons.

Problem 22

Which property of metals is most directly explained by their delocalized (free-moving) electrons?
  1. low density
  2. transparency
  3. brittleness
  4. electrical conductivity
Answer and explanation

electrical conductivity

Free-moving electrons can drift under a voltage, carrying an electric current, so metals conduct electricity.

Problem 23

Why are metals malleable (able to be hammered into sheets)?
  1. Their ions can slide past one another while the electron sea keeps holding them together
  2. Their bonds are rigid and point in fixed directions
  3. They contain no electrons to get in the way
  4. They are made of separate small molecules
Answer and explanation

Their ions can slide past one another while the electron sea keeps holding them together

When struck, layers of metal ions shift, but the mobile electron sea flows with them and keeps the metal bonded, so it bends instead of breaking.

Problem 24

Explain how metallic bonding is different from ionic bonding.
Answer and explanation

In ionic bonding, electrons are fully transferred from a metal to a nonmetal, creating positive and negative ions locked in a rigid lattice. In metallic bonding, the metal atoms' valence electrons are not transferred to any single atom but are shared among all of them in a mobile 'sea,' so the electrons stay free to move and the bond reaches in every direction.

Problem 25

The shiny luster of a polished metal surface is explained by…
  1. its rigid ionic lattice
  2. the free electrons absorbing and re-emitting light
  3. the metal's very high density
  4. electrons that are tightly bound to each atom
Answer and explanation

the free electrons absorbing and re-emitting light

The delocalized electrons readily absorb light and re-emit it, reflecting it back to give a shiny surface.

Problem 26

A salt (ionic) crystal shatters when struck, but a copper bar just bends. What is the best explanation?
  1. Salt is much softer than copper
  2. Copper is actually a gas at room temperature
  3. Copper's electron sea lets layers of ions shift while staying bonded, but shifting an ionic lattice aligns like charges that repel and split it
  4. Copper contains no chemical bonds at all
Answer and explanation

Copper's electron sea lets layers of ions shift while staying bonded, but shifting an ionic lattice aligns like charges that repel and split it

The mobile electron sea holds shifting metal ions together, while in an ionic solid a shifted layer brings like charges together, and they repel and cleave the crystal.

Problem 27

Why does a metal usually conduct better than a solid ionic crystal? Show the reasoning, not just the conclusion.
Hints

A model explains trends, but real alloys and structures affect behavior.

Answer and explanation

It has mobile delocalized electrons; ordinary ionic solids lack comparably mobile ions.

Problem 28

Can all metals be assumed to have identical strength because bonding is metallic?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

No. Composition, crystal structure, defects and processing affect mechanical properties.

Problem 29

An alloy changes a material’s composition and internal arrangementAn alloy changes a material’s composition and internal arrangementSubstitutional exampleInterstitial exampleAlloy composition and microstructure can alter deformation.AAAAAAAABAAAAAAAAA
Original topology comparison; atom sizes, spacing and alloy concentrations are illustrative rather than a specific crystal structure.
Interpret the supplied visual. What distinguishes the two selected alloy models?
Answer and explanation

The substitutional species replaces a host-site occupant; the interstitial species occupies a space between host sites in the simplified arrangement.

An alloy combines a metallic element with one or more other elements. In a substitutional model, some host sites are occupied by another species; in an interstitial model, smaller atoms occupy spaces between selected host sites. Both can influence dislocation motion and properties. Real alloys may include several phases and complex microstructures, so a uniform dot pattern is not a universal atom-by-atom picture. State composition, treatment and measured property before recommending an alloy for a design.

The substitutional species replaces a host-site occupant; the interstitial species occupies a space between host sites in the simplified arrangement.

Response criteria

  • Interpret labels, structures, axes, units and directions correctly.
  • Explain the chemistry relationship or mechanism.
  • Respect stated assumptions and distinguish observation from inference.

Problem 30

A part requires strength index ≥60 and conduction index ≥70. Materials P, Q and R score (65,80), (90,50), and (50,95). Select a feasible option and name a missing design consideration.
Answer and explanation

P satisfies both stated constraints. Q fails conduction and R fails strength. Cost, corrosion, fatigue, fabrication or service temperature could still change the decision.

P satisfies both stated constraints. Q fails conduction and R fails strength. Cost, corrosion, fatigue, fabrication or service temperature could still change the decision.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the chemical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 31

VSEPR theory predicts molecular shape based on the idea that the electron groups around a central atom…
  1. always stay at fixed 90° angles
  2. have no effect on the shape
  3. attract each other
  4. repel and spread as far apart as possible
Answer and explanation

repel and spread as far apart as possible

Electron groups are all negative, so they repel and spread out as far as possible, which sets the shape.

Problem 32

A molecule with a central atom bonded to two others and no lone pairs (like CO₂) has which shape?
  1. linear
  2. tetrahedral
  3. trigonal pyramidal
  4. bent
Answer and explanation

linear

Two electron groups push to opposite sides, giving a linear shape with a 180° bond angle.

Problem 33

A methane molecule (CH₄) is tetrahedral. What is its approximate bond angle, in degrees?
Answer and explanation

109.5 °

Four electron groups spread to the corners of a tetrahedron, giving bond angles of about 109.5°.

Problem 34

Why is a water molecule polar while carbon dioxide is nonpolar, even though both have polar bonds?
  1. Water is bent, so its bond dipoles don't cancel, while CO₂ is linear and symmetric, so its dipoles cancel
  2. Water has no polar bonds
  3. Carbon dioxide has no definite shape
  4. Water is actually an ionic compound
Answer and explanation

Water is bent, so its bond dipoles don't cancel, while CO₂ is linear and symmetric, so its dipoles cancel

Molecular polarity depends on both bond polarity and shape; water's bent shape leaves a net dipole, while CO₂'s symmetric linear shape cancels its dipoles.

Problem 35

What is a hydrogen bond, and why does it give water an unusually high boiling point?
Answer and explanation

A hydrogen bond is a strong attraction between a hydrogen atom bonded to N, O, or F in one molecule and a lone pair on the N, O, or F of a neighboring molecule. Water molecules form many hydrogen bonds with one another, so it takes a lot of extra energy — a higher temperature — to pull them apart into a gas, giving water an unusually high boiling point.

Problem 36

Ammonia (NH₃) has a central nitrogen with three bonding pairs and one lone pair. Using VSEPR, what is its molecular shape?
  1. tetrahedral
  2. trigonal pyramidal
  3. linear
  4. trigonal planar
Answer and explanation

trigonal pyramidal

The four electron groups arrange tetrahedrally, but with only three atoms attached the visible shape is trigonal pyramidal; the lone pair pushes the N–H bonds down to about 107°.

Problem 37

Why is water polar in the bent molecular model? Show the reasoning, not just the conclusion.
Hints

Compare CO₂ with bent H₂O, where dipoles do not cancel.

Answer and explanation

Its bond dipoles have components that add rather than completely cancel.

Problem 38

CH₄ has symmetric tetrahedral geometry. What does that imply for its net dipole in the simple model?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

The symmetric distribution gives no permanent net dipole.

Problem 39

Molecular polarity depends on how bond contributions combineMolecular polarity depends on how bond contributions combineCO₂: opposing contributions cancelNet dipole = 0H₂O: bent; nonzero sumOCOOHH
Original qualitative vector comparison. Connectors show bond directions and are not complete Lewis structures; water angles are schematic here.
Interpret the supplied visual. Why do two polar C–O bonds not automatically make CO₂ a polar molecule?
Answer and explanation

In the symmetric linear molecule, equal opposing contributions cancel. Geometry is needed along with bond polarity.

A dipole moment has direction as well as magnitude. Symmetry can make equal bond contributions cancel, as in an isolated ideal linear CO₂ molecule. In bent H₂O, the corresponding contributions do not cancel, producing a net molecular dipole. A bond can therefore be polar while its entire molecule has no permanent net dipole. The selected arrows point toward the negative ends as a classroom convention; a quantitative dipole calculation needs the actual charge distribution rather than these unscaled arrows alone.

In the symmetric linear molecule, equal opposing contributions cancel. Geometry is needed along with bond polarity.

Response criteria

  • Interpret labels, structures, axes, units and directions correctly.
  • Explain the chemistry relationship or mechanism.
  • Respect stated assumptions and distinguish observation from inference.

Problem 40

A molecule has four electron domains around its center, with two bonding pairs and two lone pairs. Predict electron-domain geometry and molecular shape; explain why bond angles need not be 109.5°.
Answer and explanation

The electron-domain arrangement is approximately tetrahedral and the molecular shape is bent. Lone-pair interactions and the actual chemical species alter angles; 109.5° is an ideal tetrahedral reference rather than an exact universal bond angle.

The electron-domain arrangement is approximately tetrahedral and the molecular shape is bent. Lone-pair interactions and the actual chemical species alter angles; 109.5° is an ideal tetrahedral reference rather than an exact universal bond angle.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the chemical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 41

Write the formula of magnesium nitrate.
Answer and explanation

Mg(NO₃)₂: one Mg²⁺ balances two NO₃⁻.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 42

Count oxygen atoms in 2Al₂(SO₄)₃.
Hints

Write the relationship first; substitute with consistent units.

Answer and explanation

24 atoms

2 ×3 ×4 = 24.

Problem 43

Count oxygen atoms represented by 4Ca(NO₃)₂.
Hints

List the given quantities, select a relationship, and check units before substituting.

Answer and explanation

24 atoms

4×2×3=24.

Problem 44

Why is calcium carbonate CaCO₃ rather than Ca₂(CO₃)₂?
Answer and explanation

Ca²⁺ and CO₃²⁻ balance in the smallest 1:1 ratio.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 45

Write the formula for calcium nitrate using Ca²⁺ and NO₃⁻. Show the reasoning, not just the conclusion.
Hints

The Roman numeral gives oxidation state, not number of iron atoms.

Answer and explanation

Ca(NO₃)₂; two nitrate ions balance calcium's +2 charge.

Problem 46

Name CuCl₂ assuming chloride is −1.
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Copper(II) chloride, since two chlorides require Cu²⁺.

Problem 47

Keep a polyatomic ion intact while balancing its formula ratioKeep a polyatomic ion intact while balancing its formula ratioCa²⁺ + 2 NO₃⁻ → Ca(NO₃)₂One nitrate: 1 N + 3 OTwo nitrates: 2 N + 6 OParentheses multiply the entire polyatomic group.Nitrate NO₃⁻ and nitrite NO₂⁻ are different ions.
Original stoichiometric formula construction; the reaction-style arrow indicates combining counts, not a complete solution reaction.
Interpret the supplied visual. How many oxygen atoms are represented by Ca(NO₃)₂, and why is CaNO₆ not an equivalent formula account?
Answer and explanation

Six oxygen atoms occur in two nitrate groups, along with two nitrogen atoms. CaNO₆ would lose a nitrogen and fail to represent the stated ions.

A polyatomic ion is a charged group of covalently connected atoms, such as nitrate NO₃⁻ or sulfate SO₄²⁻. Its internal formula is retained when charge balance determines how many groups are needed. Calcium nitrate therefore needs two nitrate ions, written Ca(NO₃)₂, giving one Ca, two N and six O atoms. Parentheses group the ion; they do not change its internal subscript to force neutrality. Learn common ion names and charges as linked information, and distinguish similarly named but chemically different ions.

Six oxygen atoms occur in two nitrate groups, along with two nitrogen atoms. CaNO₆ would lose a nitrogen and fail to represent the stated ions.

Response criteria

  • Interpret labels, structures, axes, units and directions correctly.
  • Explain the chemistry relationship or mechanism.
  • Respect stated assumptions and distinguish observation from inference.

Problem 48

Write the formula for iron(III) sulfate and count all atoms per formula unit. Then name N₂O₃ using molecular prefixes.
Answer and explanation

Fe³⁺ and SO₄²⁻ require Fe₂(SO₄)₃: two Fe, three S and twelve O atoms. N₂O₃ is dinitrogen trioxide. The Roman numeral and prefixes serve different bookkeeping roles.

Fe³⁺ and SO₄²⁻ require Fe₂(SO₄)₃: two Fe, three S and twelve O atoms. N₂O₃ is dinitrogen trioxide. The Roman numeral and prefixes serve different bookkeeping roles.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the chemical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 49

How many valence electrons are in NH₄⁺?
Hints

Write the relationship first; substitute with consistent units.

Answer and explanation

8 electrons

5+4−1 = 8.

Problem 50

Why is a double bond one VSEPR domain?
Answer and explanation

Its electron density points in one bond direction, despite containing two shared pairs.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 51

Count valence electrons in SO₄²⁻ using S=6 and O=6 each.
Hints

List the given quantities, select a relationship, and check units before substituting.

Answer and explanation

32 electrons

6+4×6+2=32.

Problem 52

Does nitrate repeatedly switch between three structures?
Answer and explanation

No. Resonance drawings represent one delocalized bonding structure with equivalent bonds in the idealized ion.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 53

Count total valence electrons in neutral NH₃. Show the reasoning, not just the conclusion.
Hints

Formal electron counting is a model; resonance is not rapid physical switching.

Answer and explanation

5 from N plus 3 from H=8; three bonds and one lone pair on N in the simple model.

Problem 54

Why should formal charges and octets both be checked when comparing Lewis structures?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

They help evaluate plausible electron arrangements, with known exceptions and charge constraints.

Problem 55

Formal charge is a specified electron-assignment conventionFormal charge is a specified electron-assignment conventionFormal charge = valence − nonbonding − ½(bonding)NH₄⁺: N = 5 − 0 − 4 = +1; each H = 0NHHHH
Original ammonium Lewis bookkeeping. The flat cross shows connectivity only, not the molecule’s tetrahedral geometry.
Interpret the supplied visual. Why must the formal charges in a complete NH₄⁺ drawing sum to +1?
Answer and explanation

The electron inventory represents a species with one fewer electron than the neutral-atom sum; the assignments must reproduce that total charge.

Formal charge assigns bonding electrons equally between bonded atoms: valence count minus nonbonding electrons minus half the bonding electrons. In NH₄⁺, nitrogen has four single bonds and no lone pair, giving formal charge +1; each hydrogen has zero. The sum must equal the species’ net charge. Formal charge helps compare Lewis candidates but is not a direct measurement of actual partial charge, and it is distinct from oxidation-number bookkeeping, which assigns bonding electrons differently.

The electron inventory represents a species with one fewer electron than the neutral-atom sum; the assignments must reproduce that total charge.

Response criteria

  • Interpret labels, structures, axes, units and directions correctly.
  • Explain the chemistry relationship or mechanism.
  • Respect stated assumptions and distinguish observation from inference.

Problem 56

For NH₄⁺, count valence electrons, assign nitrogen’s formal charge for four N–H single bonds and no lone pair, and distinguish that charge from molecular shape.
Answer and explanation

Total valence electrons are 5+4(1)−1=8. Nitrogen formal charge is 5−0−4=+1 and each H is zero. The flat Lewis connectivity does not specify measured angles; the common molecular arrangement is tetrahedral.

Total valence electrons are 5+4(1)−1=8. Nitrogen formal charge is 5−0−4=+1 and each H is zero. The flat Lewis connectivity does not specify measured angles; the common molecular arrangement is tetrahedral.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the chemical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Browse all courses