Chapter 2 & 7: Components of Matter and Quantum Theory

A set of flashcards covering key concepts from the notes on matter components, atomic structure, atomic models, quantum theory, and related experiments.

What are atoms?

The building blocks of matter.

Define element in chemistry.

An atom with a unique identity and characteristic physical and chemical properties (e.g., carbon).

What are subatomic particles?

Components that make up an atom.

Define a molecule.

A structure that consists of two or more atoms that are chemically bound together and displays physical/chemical properties different from the elements that compose it (e.g., CO2).

Define a compound.

Synonymous with molecule at the macroscopic level; a substance formed from two or more elements bonded together. Molecule refers to the atomic level; compound to the bulk.

Define a mixture.

A group of two or more elements/compounds that are physically intermingled but not chemically combined.

What is Heliox an example of in these notes?

A mixture (mixture of O2 and H2 as cited in the notes).

What can be separated by physical means in mixtures?

Physical mixtures; for example, a physical mixture of iron (Fe) and sulfur (S8) can be separated by a magnet; FeS forms chemically.

Differentiate heterogeneous and homogeneous mixtures.

Heterogeneous: has visible boundaries; homogeneous: no visible boundaries and usually appears uniform (a solution). Solutions involving water are aqueous solutions.

What is a solution?

A homogeneous mixture; aqueous solutions are solutions in water.

State the Law of Conservation of Mass.

Mass cannot be created or destroyed in a chemical reaction; atoms are the same before and after, so no net mass change.

What does the Law of Definite Proportions state?

A given chemical compound contains its respective elements in a fixed ratio (e.g., water is always H2O in a 2:1 ratio of H:O).

What does the Law of Multiple Proportions state?

When different compounds form from the same elements, the ratios of the elements are small whole numbers.

Outline Dalton’s Atomic Theory (basic points).

All matter consists of atoms; atoms cannot be created or destroyed in chemical reactions; atoms of a given element are identical in mass and properties; compounds are formed by combining atoms in fixed ratios.

What is an atom’s overall electrical charge?

Electrically neutral overall.

What particles are in the nucleus?

Protons (positively charged) and neutrons (neutral). The nucleus contains most of the atom’s mass.

Where are electrons located in an atom?

Outside the nucleus in the electron cloud; occupy regions around the nucleus.

Charge, mass, and location of a proton.

Charge: +1; Mass: ~1.00727 amu; Location: Nucleus.

Charge, mass, and location of a neutron.

Charge: 0; Mass: ~1.00866 amu; Location: Nucleus.

Charge, mass, and location of an electron.

Charge: -1; Mass: ~0.00054858 amu; Location: Outside the nucleus.

What is an ion?

An atom with an unequal number of protons and electrons.

Differentiate cations and anions.

Cation: positively charged ion (fewer electrons than protons). Anion: negatively charged ion (more electrons than protons).

What are isotopes?

Atoms of the same element with the same number of protons but different numbers of neutrons; different natural abundances.

What is the modern atomic model often called?

The quantum (Schrödinger) model, where electrons are treated as waves confined within boundaries set by the nucleus, described by orbitals.

State Planck’s relation for photon energy.

E = hν = hc/λ; energy of a photon increases with frequency; h = 6.626×10^-34 J·s.

What idea did Bohr introduce about atomic structure?

Electrons exist in quantized energy orbits around the nucleus (planetary model with quantized levels).

What is the Rydberg equation used for?

Describes energy differences between quantized energy levels in hydrogen: ΔE = -RH(1/nf^2 - 1/ni^2); RH = 2.18×10^-18 J.

What is meant by the ground state in hydrogen?

n = 1, the lowest energy level closest to the nucleus.

What happens when an electron absorbs a photon?

It can be excited to a higher energy level (excited state) by the energy gap.

What happens when an electron relaxes from an excited state?

It returns to the ground state by emitting a photon with energy equal to the energy gap.

What did the double-slit experiment demonstrate?

Wave-particle duality: electrons and photons show both wave-like and particle-like properties; interference patterns indicate wave behavior.

What are orbitals in the Schrödinger model?

Regions in space where there is a high probability of finding an electron; they are 3D wave functions with quantized energy levels and phases.

What is a node in an orbital?

A region where the probability of finding an electron is zero; phase changes can occur across nodes.

State the Pauli exclusion principle.

Only two electrons can occupy a single orbital.

What is the Aufbau principle?

Electrons fill the lowest-energy orbitals first to build up the ground-state electron configuration.

How do chemical bonds form according to orbital theory?

By overlap/interference of atomic orbitals, resulting in shared orbitals; a bond contains two electrons due to Pauli principle.

Why is color considered a quantum phenomenon?

Because electronic energy gaps determine which wavelengths are absorbed; e.g., beta-carotene absorbs around 450 nm, giving orange color due to complementary color absorption.

lose electrons makes it positively charged