Review of Chemistry Principles – Lecture Summary

A comprehensive set of question-and-answer flashcards covering key definitions, principles, and examples from the Review of Chemistry Principles lecture, including general chemistry, bonding, acid–base theory, organic structures, stereochemistry, reaction types, and biomolecular chemistry.

What is the scientific study that investigates the composition, properties, interactions and transformations of matter?

Chemistry.

According to the octet rule, how many valence electrons do most main-group atoms prefer to have?

Eight valence electrons.

Where are valence electrons located within an atom?

In the outermost (valence) shell.

Which orbitals (letter designations) are NOT governed by the octet rule?

d and f orbitals.

What simplified diagram uses dots or lines to represent valence-shell electrons in atoms or molecules?

A Lewis structure.

When drawing a Lewis structure, which atom is usually placed in the center of the skeletal structure?

The least electronegative atom (except hydrogen, which is never central).

During Lewis-structure electron counting, how is a negative charge treated?

Add one electron for each negative charge.

What are the two broad classes of attractive forces distinguished by whether they occur within one molecule or between different molecules?

Intramolecular forces and intermolecular forces.

Which type of chemical bond is formed by electron transfer between a metal and a non-metal?

An ionic bond.

What type of bond involves the sharing of electron pairs between atoms?

A covalent bond.

What term describes a covalent bond in which electron density is unequally shared because of differing electronegativities?

Polar covalent bond.

Give an example of a special dipole-dipole interaction that occurs when H is bonded to N, O, or F.

Hydrogen bonding.

What intermolecular force arises from temporary, induced dipoles in all atoms or molecules?

London dispersion forces (van der Waals forces).

State the Arrhenius definitions of an acid and a base.

Acid produces H⁺ in water; base produces OH⁻ in water.

According to Lewis, what is an acid?

An electron-pair acceptor.

According to Brønsted–Lowry, what acts as a proton donor?

A Brønsted–Lowry acid.

What does a lower pKa value indicate about an acid’s strength?

The acid is stronger.

Provide three common examples of strong acids.

HCl, HBr, HNO₃.

Name two strong bases that are hydroxides of group-2 metals.

Ba(OH)₂ and Mg(OH)₂.

How much do weak acids and bases dissociate in water?

They dissociate only partially (limited dissociation).

Write the mathematical expression for pH.

pH = –log[H⁺].

What is the numerical relationship between pH and pOH at 25 °C?

pH + pOH = 14.

What term describes a substance such as water that can act as either an acid or a base?

Amphoteric (or amphiprotic).

What two components must a buffer solution contain?

A weak acid (or base) and its conjugate base (or acid).

What element’s chemistry is the focus of organic chemistry?

Carbon.

How many covalent bonds can a carbon atom form?

Four covalent bonds.

Name the three kinds of multiple bonds that carbon can form with itself.

Single, double, and triple bonds.

Arrange single, double, and triple carbon–carbon bonds in order of decreasing bond length.

Single > Double > Triple (longest to shortest).

Which structural formula omits carbon and hydrogen labels, showing only bond lines and heteroatoms?

Skeletal formula (line-angle structure).

Give the general formula for an aldehyde carbonyl group.

R–C(=O)–H.

What functional group is represented by R–OH?

Hydroxyl (alcohol).

Which functional group contains a nitrogen double-bonded to carbon: R₁–C(=NH)–R₂?

Imine (Schiff base when N-substituted).

State the definition of isomers.

Compounds with the same molecular formula but different structures or arrangements.

What name is given to isomers that differ only in the connectivity of their atoms?

Constitutional isomers (structural isomers).

What type of stereoisomerism arises from restricted rotation in C=C bonds or rings and is described as cis or trans?

Geometric (cis-trans) isomerism.

Define chirality.

A property where a molecule’s mirror image is nonsuperimposable on the original.

What is a chirality center?

A tetrahedral carbon bonded to four different groups.

What term is used for stereoisomers that are non-superimposable mirror images?

Enantiomers.

Why can two enantiomers of a drug exhibit very different biological activity?

Biomolecular receptors are chiral and may bind only one enantiomer effectively (lock-and-key fit).

List the four main classes of organic reactions.

Addition, elimination, substitution, and rearrangement reactions.

In an addition reaction, how many products are formed from two reactants?

One product (no atoms left over).

What happens in an elimination reaction?

A single reactant splits into two products, often releasing a small molecule.

Define a substitution reaction.

Two reactants exchange parts to form two new products.

What is a radical?

A highly reactive species containing an atom with an unpaired electron (odd number of valence electrons).

In polar reactions, what do chemists call an electron-rich species that donates an electron pair?

A nucleophile.

What term describes an electron-poor species that accepts an electron pair?

An electrophile.

State Rule 1 for polar reaction electron flow.

Electrons move from a nucleophilic source to an electrophilic sink.

Can a nucleophile be neutral as well as negatively charged?

Yes; nucleophiles may be negative or neutral.

Can an electrophile be neutral as well as positively charged?

Yes; electrophiles may be positive or neutral.

Which rule requires that no atom exceed an octet when drawing curved-arrow mechanisms?

The octet rule must be observed (Rule 4 in polar reactions).

What class of biomolecules consists of polyhydroxy aldehydes or ketones?

Carbohydrates.

Define lipids in terms of solubility.

Naturally occurring organic molecules with limited solubility in water, extractable by nonpolar solvents.

What are proteins chemically?

Polymers of amino acids (peptides when length < 50 amino acids).

What is the structural difference between nucleosides and nucleotides?

Nucleotides are nucleosides bonded to phosphate groups.

In acid–base chemistry, what happens to acidic strength when a conjugate base is stabilized by resonance or inductive effects?

Acidity increases (lower pKa).

Why do covalent compounds generally have lower melting points than ionic compounds?

Because intermolecular forces in covalent compounds are weaker than the strong ionic lattice forces.

What simple rule of solubility is illustrated by the behavior of polar molecules like water?

“Like dissolves like” – polar solutes dissolve best in polar solvents, non-polar in non-polar solvents.

Give an example of a molecule that can hydrogen-bond to itself because it contains –OH groups.

Water (H₂O) or any alcohol such as ethanol.

What type of isomerism results when two structures have the same molecular formula but the hydroxyl group is on different carbons?

Constitutional isomerism based on different position of functional group.

Which type of stereoisomerism requires a chiral center to exist?

Enantiomerism (optical isomerism).

Name a common analgesic whose (S)-enantiomer is active while the (R)-enantiomer can be harmful.

Naproxen.

What designation (cis or trans) describes two identical substituents on the same side of a double bond?

cis.

How does the boiling point of cis-2-butene compare to trans-2-butene?

cis-2-Butene: 4 °C; trans-2-Butene: 1 °C (cis has slightly higher BP).

What term describes the spontaneous formation of H⁺ and OH⁻ from water molecules?

Autoionization of water.

Which functional group consists of a sulfur–hydrogen bond (R–SH)?

Sulfhydryl (thiol) group.

What phosphorus-containing functional group forms high-energy bonds in ATP?

Phosphoanhydride bond.

What is the general name for molecules that have identical connectivity but differ in three-dimensional arrangement and are NOT mirror images?

Diastereomers (a subset of stereoisomers distinct from enantiomers).

In nucleophilic substitution, what type of center (electron-rich or electron-poor) does the nucleophile attack?

An electron-poor (electrophilic) center.

What does the term ‘electronegativity’ refer to?

An atom’s ability to attract shared electrons in a covalent bond.