Introduction to Chemistry

• Chemistry is the study of matter and its properties as well as how matter changes
• Matter is anything that has mass and occupies space
• Properties of matter can be physical or chemical

Physical Properties

• Physical properties are those that can be observed or measured without changing the substance's composition
• Examples include color, density, melting point, and boiling point
• These properties can be intensive or extensive

Chemical Properties

• Chemical properties describe the ability of a substance to undergo changes to form new substances
• Examples include flammability, reactivity with acid, and oxidizing ability
• Observing chemical properties involves a chemical change or reaction

States of Matter

• Matter commonly exists in three states: solid, liquid, and gas
• Solids have a fixed shape and volume
• Liquids have a fixed volume but take the shape of their container
• Gases have no fixed shape or volume and can be compressed

The Periodic Table

• The periodic table is an arrangement of elements in order of increasing atomic number, grouped by similar chemical properties
• Elements are arranged in rows called periods and columns called groups (or families)

Organization of the Periodic Table

• The periodic table is organized into periods (rows) and groups (columns)
• Elements in the same group have similar chemical properties because they have the same number of valence electrons

Metals, Nonmetals, and Metalloids

• Metals are typically shiny, solid, good conductors of electricity and heat, and malleable and ductile
• Nonmetals are typically dull, may be solid, liquid, or gas, and are poor conductors of electricity and heat
• Metalloids (or semimetals) have properties intermediate between metals and nonmetals

Groups in the Periodic Table

• Group 1: Alkali Metals (Li, Na, K, Rb, Cs, Fr) - highly reactive metals
• Group 2: Alkaline Earth Metals (Be, Mg, Ca, Sr, Ba, Ra) - reactive metals
• Group 17: Halogens (F, Cl, Br, I, At) - highly reactive nonmetals
• Group 18: Noble Gases (He, Ne, Ar, Kr, Xe, Rn) - generally unreactive gases

Periodic Trends

• Periodic trends are patterns in the properties of elements as you move across or down the periodic table
• These trends include atomic radius, ionization energy, electron affinity, and electronegativity

Atomic Radius

• Atomic radius is the distance from the nucleus to the outermost electron
• Atomic radius generally decreases across a period (left to right) due to increasing nuclear charge
• Atomic radius generally increases down a group due to the addition of electron shells

Ionization Energy

• Ionization energy is the energy required to remove an electron from an atom in the gaseous phase
• Ionization energy generally increases across a period (left to right) due to increasing nuclear charge
• Ionization energy generally decreases down a group due to increasing atomic radius

Electron Affinity

• Electron affinity is the energy change that occurs when an electron is added to an atom in the gaseous phase
• Electron affinity generally increases across a period (left to right) becoming more negative (more energy released)
• Electron affinity generally decreases down a group becoming less negative (less energy released)

Electronegativity

• Electronegativity is a measure of the ability of an atom to attract electrons in a chemical bond
• Electronegativity generally increases across a period (left to right)
• Electronegativity generally decreases down a group

Chemical Bonds

• Chemical bonds are attractive forces that hold atoms together in molecules and compounds
• The main types of chemical bonds are ionic bonds, covalent bonds, and metallic bonds

Ionic Bonds

• Ionic bonds are formed by the transfer of electrons between atoms, typically between a metal and a nonmetal
• This transfer results in the formation of ions: positively charged cations and negatively charged anions

Covalent Bonds

• Covalent bonds are formed by the sharing of electrons between atoms, typically between two nonmetals
• Shared electrons are attracted to the nuclei of both atoms, holding them together

Metallic Bonds

• Metallic bonds are formed between metal atoms, where electrons are delocalized and free to move throughout the metal lattice
• This electron mobility accounts for the high electrical and thermal conductivity of metals

Intermolecular Forces

• Intermolecular forces are attractive forces between molecules
• They are weaker than chemical bonds but are important in determining the physical properties of liquids and solids
• Types of intermolecular forces include:
  • Dipole-dipole forces
  • Hydrogen bonds
  • London dispersion forces (van der Waals forces)

Dipole-Dipole Forces

• Dipole-dipole forces occur between polar molecules, which have a partially positive end and a partially negative end
• These forces arise from the attraction between the positive end of one molecule and the negative end of another

Hydrogen Bonds

• Hydrogen bonds are a special type of dipole-dipole force that occurs when hydrogen is bonded to a highly electronegative atom (N, O, or F)
• These bonds are stronger than typical dipole-dipole forces and are important in biological systems

London Dispersion Forces

• London dispersion forces are temporary, weak attractive forces that occur between all molecules, both polar and nonpolar
• They arise from instantaneous fluctuations in electron distribution, creating temporary dipoles

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms and molecules to form new substances
• These reactions are represented by chemical equations, which show the reactants and products involved

Balancing Chemical Equations

• Chemical equations must be balanced to satisfy the law of conservation of mass
• This involves adjusting the coefficients in front of the chemical formulas to ensure that the number of atoms of each element is the same on both sides of the equation

Types of Chemical Reactions

• Combination (Synthesis) Reactions: Two or more substances combine to form a single product
• Decomposition Reactions: A single compound breaks down into two or more simpler substances
• Single Displacement Reactions: One element replaces another element in a compound
• Double Displacement Reactions: Two compounds exchange ions or groups of ions
• Combustion Reactions: A substance reacts rapidly with oxygen, usually producing heat and light

Stoichiometry

• Stoichiometry is the quantitative study of the relationships between reactants and products in chemical reactions
• It involves using balanced chemical equations to calculate the amounts of reactants and products involved in a reaction

Molar Mass

• Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol)
• It is numerically equal to the atomic mass or molecular mass of the substance

Mole Concept

• The mole (mol) is the SI unit for the amount of substance
• One mole contains Avogadro's number (6.022 x 10^23) of particles (atoms, molecules, ions, etc.)

Limiting Reactant

• The limiting reactant is the reactant that is completely consumed in a chemical reaction
• It determines the maximum amount of product that can be formed

Percent Yield

• Percent yield is the ratio of the actual yield (amount of product obtained) to the theoretical yield (amount of product calculated from stoichiometry), expressed as a percentage
• (Actual Yield / Theoretical Yield) * 100%