Chapter 1 · Building Blocks · Ten playable problems

Ch 1 · P1 — Why atoms bond

PROBLEM 01 · BUILDING BLOCKS — THE ENERGY WELL

Why do atoms form bonds? Drag the two nuclei apart and together, watch the total energy of the whole system move, then click the separation a bond actually holds.

Live model

stable arrangement = minimum total energyDrag the atoms together and apart. Then click the separation where a bond actually sits.

Ch 1 · P2 — Transfer or share

PROBLEM 02 · BUILDING BLOCKS — ELECTRON ROUTING

Route one electron transfer and one shared pair. The electrons draw themselves — then the bond names follow.

Live model

ionic = transfer | covalent = sharePick a route, then click the model it belongs to.

Ch 1 · P3 — Two polar bonds, one survivor

PROBLEM 03 · BUILDING BLOCKS — VECTOR SUM

Carbon dioxide and water both carry polar covalent bonds. Bend water down to 104.5 degrees and watch which molecule keeps a net dipole.

Live model

Target 104.5°

two identical bond vectors, summed by geometryBend the water molecule. Watch the two bond arrows add — then park it at 104.5 degrees.

Ch 1 · P4 — The four site network

PROBLEM 04 · BUILDING BLOCKS — THE NETWORK

Click all four connection sites — two hydrogens that donate, two lone pairs that accept. Then click the line that is actually a hydrogen bond.

Live model

0 / 4 sites

2 donors + 2 acceptors = 4 connections per moleculeFill all four sites: two hydrogens that donate, two lone pairs that accept.

Ch 1 · P5 — Gallons to grams

PROBLEM 05 · BUILDING BLOCKS — UNIT CHAIN RAIL

Convert 10 gallons of water to pounds and then grams. Place each factor so the units cancel, and flip the one that lands upside down.

Live model

One factor is a decoy

10 gal × 8.34 lb/gal × 453.6 g/lbPlace the factor whose bottom unit cancels what flows in. One factor does not belong on this rail.

Ch 1 · P6 — Molar mass, then moles

PROBLEM 06 · BUILDING BLOCKS — THE MOLE BRIDGE

Stack the atoms of CaCO₃ until the molar mass is right, then carry 50 grams across the bridge.

Live model

50 g given

molar mass = Σ (atomic mass × count)Stack the atoms in CaCO₃, then carry 50 grams across the bridge.

Ch 1 · P7 — Basin water in moles

PROBLEM 07 · BUILDING BLOCKS — THREE GATES

A cooling tower basin holds 5,000 gallons. Open the three gates in the order the units allow and count the moles of water.

Live model

5,000 gal → lb → g → molOpen the gates in the order the units allow. Each one has to swallow the unit arriving at it.

Ch 1 · P8 — One compound, both bonds

PROBLEM 08 · BUILDING BLOCKS — THE HYBRID LATTICE

Calcium carbonate carries two kinds of bonding in one crystal. Assign each one to the place it actually holds.

Live model

covalent inside the ion · ionic between the ionsPick a bond type, then click the part of the lattice it holds together.

Ch 1 · P9 — Charge counts the loss

PROBLEM 09 · BUILDING BLOCKS — THE VALENCE DRAWER

Pull the valence electrons off each metal and read the charge left behind. The group number tells you how many will come.

Live model

charge = valence electrons removedGroup one gives up one. Group two gives up two. Pull the valence electrons off and read what is left.

Ch 1 · P10 — Why water stays tense

PROBLEM 10 · BUILDING BLOCKS — CAUSE TO CONSEQUENCE

Install oxygen's two lone pairs, let repulsion bend the geometry, then walk the test probe around and find the charge field the molecule locks in.

Live model

lone pairs → repulsion → bent geometry → net polarity0 of 2 lone pairs installed. Unshared electrons take up room too.

Problem set

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Problem 1
Why do atoms form bonds? Your answer should reference lower total energy, not attraction alone.
Authored answer
Atoms bond when the resulting arrangement places the combined system at a lower total energy than the separated atoms. Incomplete valence shells are high-energy states; bonding allows atoms to fill or empty their outer shells and settle into stability.
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Problem 2
What distinguishes an ionic bond from a covalent bond? Describe each in terms of what happens to the electrons.
Authored answer
In ionic bonding, electrons are transferred from one atom to another, creating oppositely charged ions that attract. In covalent bonding, electrons are shared between atoms. The distinction is transfer vs. sharing.
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Problem 3
Both water (H₂O) and carbon dioxide (CO₂) contain polar covalent bonds, yet only water is a polar molecule. Why?
Authored answer
CO₂ is linear: its two polar bonds point in opposite directions and cancel. Water is bent at 104.5°, so its polar bonds point in the same general direction and the charge imbalance survives. Geometry determines whether local polarity becomes molecular polarity.
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Problem 4
What is the Hydrogen-Bond Network? Is it made of true chemical bonds? Why does it matter that each water molecule can participate in up to four hydrogen bonds?
Authored answer
The Hydrogen-Bond Network is the persistent web of intermolecular attractions between water molecules, formed by the partial positive charge on hydrogen attracting the partial negative charge on a neighboring oxygen. It is not a true chemical bond, it is roughly 1/10th the strength of a covalent bond. Because each molecule can form up to four hydrogen bonds, the network is continuous and interconnected, giving water its collective behavior.
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Problem 5
Using dimensional analysis, convert 10 gallons of water to (a) pounds and (b) grams. Show units cancelling at each step.
Authored answer
(a) 10 gal × 8.34 lb/gal = 83.4 lb. (b) 83.4 lb × 453.6 g/lb = 37,830 g.
Problem 6
Calculate the molar mass of CaCO₃ using the periodic table. How many moles are in 50 grams?
Authored answer
Ca: 40.08 g/mol, C: 12.01 g/mol, O: 16.00 g/mol. (40.08)+(12.01)+ (3×16.00) = 100.09 g/mol. 50 g ÷ 100.09 g/mol = 0.50 mol.
Problem 7
A cooling tower basin holds 5,000 gallons of water. How many moles of water is that? Show the full conversion chain.
Authored answer
5,000 gal × 8.34 lb/gal = 41,700 lb. 41,700 lb × 453.6 g/lb = 18,915,120 g. 18,915,120 g ÷ 18.015 g/mol = 1,050,000 mol (1.05 × 10⁶ mol).
Problem 8
Calcium carbonate (CaCO₃) contains both ionic and covalent bonds within the same compound. Identify which bonds are ionic and which are covalent, and explain why this combination produces a crystal lattice that is difficult to pull apart.
Authored answer
Covalent bonds: the three C–O bonds within the carbonate ion (CO₃²⁻), forming a rigid, symmetric internal framework. Ionic bond: the electrostatic attraction between Ca²⁺ and CO₃²⁻. The rigid covalent unit does not deform, and the strong ionic attraction locks these units into a dense, interlocking crystal lattice, exceptionally stable and difficult to dissolve.
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Problem 9
Using the periodic table, explain why sodium (Group 1) and calcium (Group 2) both form positive ions, but calcium’s ion carries a +2 charge while sodium’s carries +1. Connect your answer to valence electrons.
Authored answer
Sodium (Group 1) has one valence electron and donates it to achieve a full outer shell, producing Na⁺. Calcium (Group 2) has two valence electrons and must donate both to reach stability, producing Ca²⁺. Ion charge directly reflects the number of valence electrons an atom must lose.
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Problem 10
The chapter describes the water molecule as “asymmetric, polar, and carrying stored electrical tension.” In 2–3 sentences, explain how each of these properties traces back to oxygen’s lone electron pairs and the resulting molecular geometry.
Authored answer
Oxygen carries two lone electron pairs that repel the bonding pairs shared with hydrogen, forcing the molecule into a bent shape (104.5°) rather than a straight line. This asymmetry means the two polar O–H bonds do not cancel, making the molecule polar. The permanent separation of partial positive and partial negative charge is the “stored electrical tension,” it is locked into the geometry by the lone pairs. This is the basis of hydrogen bonding in water.
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