Y1 · I · #26Chemical bonds

Testing

Testing Your Knowledge: Chemical Bonds

You've spent this unit exploring ionic, covalent, and metallic bonding — how atoms stick together, why some compounds dissolve while others don't, and why shape and polarity matter so much in chemistry. This lesson is a quick checkpoint: a short practice set to see what's stuck and what needs another look before we move on.

Quick Recap

Before you dive in, remind yourself of a few key ideas:

Simple molecular (covalent) compounds tend to have low melting and boiling points because only weak intermolecular forces need to be overcome, not strong bonds (Talbot, p.167).
Compounds held together mainly by London (dispersion) forces (like I₂) dissolve well in non-polar solvents but poorly in water, while those capable of hydrogen bonding (like sugars or amines) often dissolve well in water — especially if they're small or can form several hydrogen bonds (Talbot, p.167).
Molecular compounds generally don't conduct electricity, even when molten, because they contain no free ions or delocalised charge carriers (Talbot, p.167).
A molecule's overall polarity depends on both bond polarity and molecular shape — dipoles can cancel if arranged symmetrically (

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Source excerpts

From Chemistry for the IB Diploma 3e · Talbot

p.167relevance 7.4

S2.2 The covalent model 155 ■Physical properties of simple molecular compounds ■ Simple molecular compounds are gases, liquids or soft solids with low melting points. ■ Most simple covalent compounds whose intermolecular forces are mainly London (dispersion) f orces (for example, iodine and the halogenoalkanes) are poorly soluble in water, but are soluble in less polar or non-p…

p.642relevance 5.3

630 R3: What are the mechanisms of chemical change? 630 H3C H3C H3C H3C CH3 CH3 O 2NR3 OH OHO + 2NR3+ hf ■Figure R3.88 Formation of radicals from the photoinitiator mixture in a dental composite The radicals then undergo a radical addition reaction with an alkene on the end of ‘ bis- GMA ’ monomer (Figure R3.89). This starts the polymerization process which hardens the composit…

p.159relevance 5.1

S2.2 The covalent model 147 Deduce which of the difluorobenzene molecules shown is non-polar (has zero dipole moment). 03_29 Cam/Chem AS&A2 Barking Dog Art F F F F F FA B C Answer Compound C, 1,4-difluorobenzene. In compound C, the C–F dipoles are on opposite sides of the benzene ring so their two equal dipoles oppose each other and cancel. In molecules A and B, the C–F dipoles…

p.307relevance 4.7

early 20th century that chemists started to investigate how infrared radiation interacted with matter. The first commercial infrared spectrometers were manufactured in the USA during the 1940s. Infrared spectroscopy is used in modern breath testing machines to identify individuals who drive while under the influence of alcohol. Greenhouse gases The absorption of infrared radiat…