Principles of Chemistry I: Ionic Compounds and Nomenclature

Ionic Compound

A compound that contains ions and is held together by ionic bonds.

Cation

A positively charged ion formed when a metal loses electrons.

Anion

A negatively charged ion formed when a nonmetal gains electrons.

Sodium Chloride

An ionic compound formed from one Na atom giving up one electron to form a Na+ ion and one Cl atom accepting that electron to form a Cl- ion.

Calcium Chloride

An ionic compound formed from one Ca atom giving up two electrons to form a Ca2+ ion and two Cl atoms each accepting one electron to form two Cl- ions.

Properties of Ionic Compounds

Typically solids with high melting and boiling points, nonconductive in solid form, and conductive in molten form.

Melting Point of Sodium Chloride

Sodium chloride melts at 801 °C and conducts electricity when molten.

Molecular Formula

Represents the actual number of each type of atom in a molecule of a compound.

Ionic Formula

Represents the ratio of ions in an ionic compound, formed from the electrostatic attraction between cations and anions.

Example of Ionic Formula

For sodium chloride (NaCl), the ionic formula indicates a 1:1 ratio of sodium ions (Na⁺) to chloride ions (Cl⁻).

Key Differences between Molecular and Ionic Formulas

Molecular formulas show the exact number of each type of atom in a single molecule, while ionic formulas show the ratio of ions in the compound.

Polyatomic Ions

Ionic compounds may contain polyatomic ions as the cation, the anion, or both.

Hydrate

A compound, often ionic, that contains one or more water molecules bound within its crystals.

Naming Ionic Compounds

Name the cation first, followed by the name of the anion.

Monoatomic Cation

Given the name of the element, e.g., Ca2+: Calcium.

Monoatomic Anion

Given the name of the element with its ending replaced by the suffix -ide, e.g., Cl-: Chloride.

Oxyanion Naming

When a nonmetal forms two oxyanions, -ate is used for the ion with the larger number of oxygen atoms and -ite for the smaller.

Variable Charge Metal Ions

Most transition metals can form two or more cations with different charges, specified by a Roman numeral in parentheses after the name.

Example of Ionic Compound with Polyatomic Ion

Ca2+ and PO43- forms Ca3(PO4)2, where three Ca2+ ions give six positive charges and two PO43- ions give six negative charges.

Covalent Bonding

Atoms in molecular compounds are held together by covalent bonds, where electrons are shared between atoms.

Discrete Molecules

Molecular compounds consist of discrete molecules rather than extended lattices.

States of Molecular Compounds

They can exist in various states—solid, liquid, or gas—depending on temperature and pressure.

Low Melting and Boiling Points

Molecular compounds generally have lower melting and boiling points compared to ionic compounds.

Water (H₂O)

Essential for life, consisting of two hydrogen atoms covalently bonded to one oxygen atom.

Methane (CH₄)

A major component of natural gas, consisting of one carbon atom bonded to four hydrogen atoms.

Glucose (C₆H₁₂O₆)

A simple sugar and important energy source for cells, consisting of six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.

Hydrochloric Acid (HCl)

Consists of one hydrogen atom covalently bonded to one chlorine atom in its molecular form.

Sulfur Dioxide (SO₂)

A gas with one sulfur atom bonded to two oxygen atoms, used in the preservation of dried fruits.

Phosphoric Acid (H₃PO₄)

Contains three hydrogen atoms, one phosphorus atom, and four oxygen atoms, used in fertilizers and food flavorings.

Anhydrous Compound

Substance without water molecules.

Stoichiometric Coefficient

Number indicating quantity of molecules.

Greek Prefix

Denotes number of molecules in hydrates.

Binary Molecular Compound

Compound formed from two nonmetals.

Nomenclature Prefixes

Prefixes indicating number of atoms.

Acid

Substance releasing H+ ions in water.

Binary Acid

Acid containing hydrogen and one nonmetal.

Oxyacid

Acid containing hydrogen, oxygen, and another element.

Wave

Oscillation transporting energy through space.

Speed of Light

Constant speed of electromagnetic waves in vacuum.

Wavelength (λ)

Distance between consecutive wave peaks.

Frequency (ν)

Number of wavelengths passing a point per second.

Amplitude

Height of wave from peak to trough.

Hertz (Hz)

Unit of frequency, cycles per second.

Electromagnetic Spectrum

Range of all types of electromagnetic radiation.

Interference Patterns

Patterns formed by overlapping waves.

Standing Waves

Waves constrained in a fixed region.

Destructive Interference

Waves cancel each other out.

Constructive Interference

Waves amplify each other.

Wave-Particle Duality

Concept that light exhibits both wave and particle properties.

Newtonian Particles

Light described as tiny particles by Newton.

Oxyacid Naming

Replace -ate with -ic, -ite with -ous.

Light Wavelength Calculation

Use c = λν to find wavelength.

Light Frequency Calculation

Use c = λν to find frequency.

Greek Prefix Mono-

Used when one atom of first element present.

Periodic Table Position

Determines order of naming elements.

Wave Properties

Characteristics include wavelength, frequency, amplitude.

Quantization

Limitation to specific discrete values, not continuous.

Nodes

Points in standing waves with zero displacement.

Two-Dimensional Standing Waves

Vibrational patterns on flat surfaces exhibiting nodes.

Radial Nodes

Circular nodal lines in two-dimensional standing waves.

Angular Nodes

Radial lines in two-dimensional standing waves.

Blackbody

Ideal body absorbing all electromagnetic radiation.

Blackbody Radiation

Thermal radiation emitted by a perfect blackbody.

Ultraviolet Catastrophe

Discrepancy in predicted vs. observed UV radiation.

λmax

Wavelength at which blackbody radiation peaks.

Planck's Constant

Constant relating energy and frequency, h = 6.626 × 10−34 J·s.

Photoelectric Effect

Ejection of electrons from metal by light.

Threshold Frequency

Minimum frequency required to eject electrons.

Photon

Particle of light with quantized energy.

Line Spectra

Discrete wavelengths emitted by excited gases.

Continuous Spectrum

Unbroken series of wavelengths from heated solids.

Emission Line

Single wavelength of light emitted by atoms.

Balmer Equation

Empirical formula for hydrogen's spectral lines.

Kinetic Energy of Electrons

Depends on frequency of incident light.

Thermodynamic Equilibrium

State where a blackbody emits radiation uniformly.

Vibrational Frequencies

Increase with temperature in vibrating atoms.

Spectral Distribution

Intensity of light versus wavelength graph.

Cosmic Microwave Background

Radiation from the early universe, a blackbody example.

Excited Neon Atoms

Source of light in neon signs.

Temperature and Wavelength

Higher temperatures shift λmax to shorter wavelengths.

Experimental Observations

Data used to derive theoretical expressions.

Johann Balmer

Derived an equation for hydrogen's visible wavelengths.

Rydberg Constant

R∞ = 1.097 × 10^7 m−1.

Niels Bohr

Proposed the Bohr model of the hydrogen atom.

Bohr Model

Explains hydrogen's emission spectra using quantization.

Quantum Mechanics

Modern physics framework replacing classical mechanics.

Ground State

Lowest energy state of an atom (n = 1).

Excited State

Higher energy state with n > 1.

Photon Absorption

Electron moves to a higher energy orbit.

Photon Emission

Electron falls to a lower energy orbit.

Energy Difference (ΔE)

Reflects energy absorbed or emitted by electron.

Quantized Energies

Only discrete energy values are allowed.

Bohr's Energy Equation

Describes energy levels in hydrogen atom.

De Broglie Wavelength

λ = h / (mv), relates wavelength to particle properties.

Planck's Constant (h)

Fundamental constant in quantum mechanics.

Electromagnetic Radiation

Energy waves including visible light and others.

Classical Electromagnetism

Predicts continuous radiation from accelerating charges.

Quantum Numbers

Integer values defining electron energy states.

Louis de Broglie

Extended wave-particle duality to matter.

Bohr's Limitations

Fails for multi-electron atoms and electron interactions.