Learn: AP Chemistry Practice

Which type of light has the highest frequency and energy?

Light with the shortest wavelength. Frequency and energy increase as wavelength decreases.

What happens when an electron moves from a lower energy level to a higher energy level?

The electron absorbs energy to move farther away from the nucleus.

What happens when an electron moves from a higher energy level to a lower energy level?

The electron releases energy, usually in the form of light.

What is the electron configuration of calcium (Ca)?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² or [Ar] 4s².

What is the electron configuration of chlorine (Cl⁻)?

1s² 2s² 2p⁶ 3s² 3p⁶ or [Ar] (18 total electrons).

What is Hund's Rule?

Electrons fill empty orbitals individually before pairing up with parallel spins.

How many valence electrons does phosphorus have, and what is its electron configuration?

5 valence electrons; configuration is [Ne] 3s² 3p³.

What happens to bond polarity when the electronegativity difference between two atoms increases?

Bond polarity increases as one atom attracts shared electrons more strongly.

What type of bond forms between atoms with very different electronegativities?

An ionic bond, formed by transferring electrons rather than sharing them.

Which bond is least polar: H—F, C—O, Cl—Cl, or N—H?

Cl—Cl, because identical electronegativities mean electrons are shared equally.

What is the difference between a polar bond and a polar molecule?

Polar bonds have unequal sharing; polar molecules have uncancelled bond dipoles.

Why is CO₂ nonpolar even though its C=O bonds are polar?

Its linear, symmetrical shape causes the bond dipoles to cancel out.

Why is H₂O polar?

Its bent shape prevents O—H bond dipoles from canceling, creating a net dipole.

How does atomic radius change moving from left to right across a period?

Radius decreases due to increasing nuclear charge pulling electrons closer.

How does atomic radius change moving down a group?

Radius increases because additional energy levels place electrons farther away.

Which is smaller: Na or Na⁺? Explain why.

Na⁺ is smaller because losing its outermost electron reduces its cloud.

What does it mean for two atoms or ions to be isoelectronic?

They have the same number of electrons despite different proton numbers.

Which is smaller: Mg²⁺ or O²⁻? Explain why.

Mg²⁺ is smaller due to more protons exerting stronger electron attraction.

What happens to bond length and bond strength as bond order increases?

Bond length decreases while bond strength and energy increase.

How many sigma and pi bonds are in a double bond?

One sigma bond and one pi bond.

How many sigma and pi bonds are in a triple bond?

One sigma bond and two pi bonds.

How many pi electrons are present in benzene (C₆H₆)?

6 pi electrons, with each carbon contributing one delocalized electron.

What is the formula used to calculate reaction enthalpy using bond energies?

ΔH = Bonds broken minus Bonds formed.

What is the difference between intramolecular and intermolecular forces?

Intramolecular forces are within molecules; intermolecular forces are between separate molecules.

What is the formula for calculating formal charge?

Valence electrons minus nonbonding electrons minus number of bonds.

What is resonance in a Lewis structure?

Multiple valid structures formed by moving electrons without changing atom arrangements.

What is an expanded octet? Give an example.

More than 8 electrons around an atom, e.g., sulfur in SF₆.

What is the molecular geometry of NH₃, and why?

Trigonal pyramidal, because nitrogen has three bonding pairs and one lone pair.

What is the molecular geometry of SF₄, and why?

Seesaw, because sulfur has four bonding pairs and one lone pair.

Why does oxygen have a lower first ionization energy than nitrogen?

Electron repulsion from a paired 2p orbital makes removal easier.