Chemistry: Atomic Structure and Bonding

Atomic Structure

• Atomic model:
  • Protons (positive charge) in the nucleus
  • Neutrons (no charge) in the nucleus
  • Electrons (negative charge) in energy levels (shells) around the nucleus
• Subatomic particles:
  • Proton: +1 charge, 1 amu (atomic mass unit)
  • Neutron: 0 charge, 1 amu
  • Electron: -1 charge, negligible mass
• Atomic number (Z): number of protons in an atom's nucleus
• Mass number (A): total number of protons and neutrons in an atom's nucleus

Chemical Bonding

• Types of bonds:
  • Ionic bond: electrostatic attraction between oppositely charged ions
  • Covalent bond: sharing of electrons between atoms
• Bonding theories:
  • Electronegativity: ability of an atom to attract electrons
  • Electronegativity difference: predicts bond type (ionic or covalent)

Periodic Table

• Organization:
  • Rows: periods (horizontal)
  • Columns: groups (vertical)
• Periodic trends:
  • Atomic radius decreases from left to right across a period
  • Electronegativity increases from left to right across a period
• Blocks:
  • s-block: first two columns (alkali metals and alkaline earth metals)
  • p-block: last six columns (nonmetals and metalloids)

Chemical Reactions

• Types of reactions:
  • Synthesis reaction: two substances combine to form a new compound
  • Decomposition reaction: one substance breaks down into two or more substances
  • Single displacement reaction: one element replaces another in a compound
  • Combustion reaction: reaction with oxygen, often producing heat and light
• Reaction rates:
  • Factors affecting rate: concentration, temperature, surface area, catalysts

Acids and Bases

• Arrhenius theory:
  • Acid: substance that donates a proton (H+)
  • Base: substance that accepts a proton
• pH scale:
  • pH = -log[H+]
  • Acidic: pH < 7
  • Basic: pH > 7
  • Neutral: pH = 7

Reactivity of Metals

• Reactivity series:
  • Metals listed in order of reactivity (most reactive to least reactive)
  • Reacts with oxygen, water, and acids to form compounds
• Extraction of metals:
  • Methods: electrolysis, smelting, and refining

Writing the Formula

• Formula writing rules:
  • Cations (positive ions) first
  • Anions (negative ions) second
  • Polyatomic ions: retain their charge and formula
• Formula types:
  • Molecular formula: actual number of atoms in a molecule
  • Empirical formula: simplest whole-number ratio of atoms in a molecule

Precipitation Reactions

• Definition: reaction resulting in the formation of an insoluble solid (precipitate)
• Conditions for precipitation:
  • High concentration of reactants
  • Presence of an electrolyte
• Net ionic equation: shows only the species participating in the reaction

Balancing the Equation

• Steps to balance an equation:
  1. Write the unbalanced equation
  2. Count the atoms of each element on both sides
  3. Add coefficients in front of formulas to balance the equation
• Balanced equation: number of atoms of each element is equal on both sides

Hydrocarbons

• Definition: compounds containing only carbon and hydrogen atoms
• Types of hydrocarbons:
  • Saturated (single bonds only): alkanes
  • Unsaturated (multiple bonds): alkenes and alkynes
• Functional groups:
  • Alkyl group: hydrocarbon chain attached to a functional group
  • Substituent: atom or group of atoms replacing a hydrogen atom

Atomic Structure

• Atomic model consists of protons, neutrons, and electrons
• Protons have a positive charge, neutrons have no charge, and electrons have a negative charge
• Electrons are arranged in energy levels (shells) around the nucleus
• Atomic number (Z) is the number of protons in an atom's nucleus
• Mass number (A) is the total number of protons and neutrons in an atom's nucleus

Chemical Bonding

• Ionic bonds form through electrostatic attraction between oppositely charged ions
• Covalent bonds form through the sharing of electrons between atoms
• Electronegativity is the ability of an atom to attract electrons
• Electronegativity difference predicts bond type (ionic or covalent)

Periodic Table

• The periodic table is organized into rows (periods) and columns (groups)
• Atomic radius decreases from left to right across a period
• Electronegativity increases from left to right across a period
• The s-block consists of the first two columns (alkali metals and alkaline earth metals)
• The p-block consists of the last six columns (nonmetals and metalloids)

Chemical Reactions

• Synthesis reactions involve two substances combining to form a new compound
• Decomposition reactions involve one substance breaking down into two or more substances
• Single displacement reactions involve one element replacing another in a compound
• Combustion reactions involve reaction with oxygen, often producing heat and light
• Factors affecting reaction rate include concentration, temperature, surface area, and catalysts

Acids and Bases

• Acids donate a proton (H+), while bases accept a proton
• pH is measured on a scale from 0 to 14, with 7 being neutral
• Acidic solutions have a pH < 7, basic solutions have a pH > 7

Reactivity of Metals

• The reactivity series lists metals in order of reactivity (most reactive to least reactive)
• Metals react with oxygen, water, and acids to form compounds
• Metals are extracted through electrolysis, smelting, and refining

Writing the Formula

• Cations are written first, followed by anions
• Polyatomic ions retain their charge and formula
• Molecular formula shows the actual number of atoms in a molecule
• Empirical formula shows the simplest whole-number ratio of atoms in a molecule

Precipitation Reactions

• Precipitation reactions result in the formation of an insoluble solid
• Conditions for precipitation include high concentration of reactants and presence of an electrolyte
• Net ionic equations show only the species participating in the reaction

Balancing the Equation

• The steps to balance an equation include writing the unbalanced equation, counting atoms, and adding coefficients
• A balanced equation has the same number of atoms of each element on both sides

Hydrocarbons

• Hydrocarbons are compounds containing only carbon and hydrogen atoms
• Saturated hydrocarbons (alkanes) have single bonds only
• Unsaturated hydrocarbons (alkenes and alkynes) have multiple bonds
• Alkyl groups are hydrocarbon chains attached to a functional group
• Substituents are atoms or groups of atoms replacing a hydrogen atom