chem 1

What is the difference between a hypothesis and a theory?

A hypothesis is a tentative explanation tested through experiments, while a theory explains broad sets of results and observations.

What is a scientific law?

A concise description of a natural phenomenon or process.

Which two laws does Dalton’s atomic theory explain?

Law of definite proportions (Proust) and law of multiple proportions (Dalton)

Proust

Law of definite proportions

Dalton

law of multiple proportions

What does the COAST problem-solving method stand for?

Collect, Analyze, Solve, Think.

What are intensive properties? Give examples.

Independent of amount of substance (e.g., density, boiling point).

What are extensive properties? Give examples.

Depend on amount of substance (e.g., mass, volume)

What is the difference between physical and chemical properties?

Physical can be observed without changing substance; chemical can only be observed via reactions.

What is the formula for density?

d = m/v

Homogeneous

uniform composition (solutions)

Heterogeneous

non-uniform composition

Which separation technique uses volatility differences?

Distillation

What is sublimation?

Solid to Gas

What is deposition?

Gas to Solid

What does an empirical formula represent?

The simplest ratio of ions in an ionic compound.

kinetic energy 

energy of motion

potential energy

energy of position/composition

What does the law of conservation of energy state?

Energy cannot be created or destroyed.

Precision

repeatability

Accuracy

closeness to true value

What is dimensional analysis?

Converting units using conversion factors.

mean

average value

Standard deviation

variability in data.

Which experiments determined the charge and mass of the electron?

J. J. Thomson’s cathode-ray tube (charge-to-mass ratio) and Millikan’s oil-drop experiment (charge).

What did Rutherford’s gold foil experiment show?

That atoms have a small, dense, positively charged nucleus containing most of the atom’s mass.

What is the atomic number (Z)

The number of protons in the nucleus.

What is the mass number (A)

The total number of protons and neutrons in the nucleus

What are isotopes?

Atoms with the same number of protons (Z) but different numbers of neutrons

What does the symbol A/Z X represent?

A nucleus/atom with mass number A, atomic number Z, and element symbol X.

How are elements arranged in the periodic table?

By increasing atomic number and recurring chemical properties.

What is the difference between a cation and an anion?

Cation is positive while anion is negative

Which groups are main group elements?

Groups 1, 2, and 13–18.

Which groups are transition metals?

Groups 3 to 12

What are the general properties of metals?

Malleable, ductile, good conductors, form cations.

What are the general properties of NONmetals?

Found in all states, poor conductors, form anions

What are metalloids?

Elements with properties of both metals and nonmetals.

How do you calculate average atomic mass?

Multiply isotope mass × percent abundance, then sum

What is a mole?

SI unit for amount of substance; contains 6.022×10236.022 \times 10^{23}6.022×1023 particles.

What is molar mass?

The mass of one mole of a substance in grams.

What is molecular mass?

Sum of the average atomic masses of all atoms in a molecule.

What is formula mass?

The mass of the simplest neutral unit of an ionic compound.

What does mass spectrometry measure?

The m/z values of ions, used to determine molar masses

What two properties describe electromagnetic waves?

Wavelength (λ) and frequency (ν)

What is the speed of light in a vacuum?

2.998×10^8m/s.

What does quantum theory state about energy in atoms?

Atoms have discrete energy levels and absorb/emit photons.

Who explained blackbody radiation with quanta?

Planck

Who explained the photoelectric effect with photons?

Einstein.

What causes atomic emission and absorption spectra?

Electron transitions between energy levels

What did De Broglie propose about electrons?

They behave like waves (matter waves)

What is the Heisenberg uncertainty principle?

It’s impossible to know both the position and momentum of an electron precisely.

What does Schrödinger’s wave function (ψ) describe?

The probability region (orbital) where an electron is found.

Name the four quantum numbers and what they represent.

• n = size/energy level

• ℓ = shape

• mℓ = orientation

• ms = spin

What does the Pauli exclusion principle state?

No two electrons can share the same four quantum numbers.

What is the Aufbau principle?

Electrons fill lowest-energy orbitals first

What is Hund’s rule?

Orbitals in the same subshell are filled singly before pairing, with parallel spins.

What are valence vs core electrons?

Valence = outermost shell; Core = inner filled shells.

How does atomic size change in the periodic table?

Increases down a group, decreases across a period.

How do cations and anions differ in size from their parent atoms?

Cations are smaller; Anions are larger.

What is effective nuclear charge (Zeff)?

The net nuclear charge felt by valence electrons, reduced by shielding

What is ionization energy (IE)

Energy needed to remove one mole of electrons from one mole of gas-phase atoms.

How does ionization energy trend in the periodic table?

Increases across a period, decreases down a group.

What are photoelectron spectra used for?

Identifying elements and determining electron configurations.

What is electron affinity (EA)?

The energy change when an atom/ion in the gas phase gains an electron

What does a negative EA value mean?

Energy is released when the atom gains an electron.