Chemistry Chapter: Periodic Table & Electron Configs

Structure of the Periodic Table

• Organized into groups (columns) and periods (rows).
• Groups contain elements with similar chemical properties; numbered 1 to 18.
• Periods represent energy levels of electrons; numbered 1 to 7.
• Metals are located on the left side and in the center, characterized by luster, conductivity, and ductility.
• Nonmetals are found on the right side, generally poor conductors and often brittle in solid form.
• Metalloids (semi-metals) are located along the zig-zag line between metals and nonmetals, exhibiting mixed properties.

Electron Configurations

• Electron configurations describe the distribution of electrons among atomic orbitals.
• Follow the Aufbau principle, filling from lower to higher energy levels:
  • Example: Oxygen (O) - 1s² 2s² 2p⁴.
• For ions, adjust configurations based on the charge; cations lose electrons, anions gain:
  • Example: Na⁺ - 1s² 2s² 2p⁶ (loses one electron).

Definitions of Ions

• Ion: An atom or molecule with a net electric charge due to loss or gain of one or more electrons.
• Anion: A negatively charged ion, formed by gaining electrons (e.g., Cl⁻).
• Cation: A positively charged ion, formed by losing electrons (e.g., Na⁺).
• Monatomic Ion: An ion consisting of a single atom (e.g., Na⁺).
• Polyatomic Ion: An ion made up of two or more atoms bonded together (e.g., SO₄²⁻).

Formation of Ions

• Ions are formed through ionization, which involves the transfer of electrons between atoms.
• Metals tend to lose electrons and form cations.
• Nonmetals tend to gain electrons and form anions.

Valence of Common Ions

• Valence indicates the ability of an atom to bond based on its electron configuration.
• Common ions include:
  • Na⁺: valence of +1
  • Cl⁻: valence of -1
  • Ca²⁺: valence of +2
  • SO₄²⁻: valence of -2

Ionic Formula

• An ionic formula represents the ratio of ions in the compound.
• It is determined by balancing the total positive charge with total negative charge.
• Example: NaCl consists of Na⁺ and Cl⁻ in a 1:1 ratio.

Law of Conservation of Mass

• States that mass is neither created nor destroyed in a chemical reaction.
• The total mass of reactants equals the total mass of products.

Salt Formed in Neutralization Reactions

• A neutralization reaction between an acid and a base produces a salt and water.
• Example: From hydrochloric acid (HCl) and sodium hydroxide (NaOH), sodium chloride (NaCl) is formed.

Exothermic and Endothermic Reactions

• Exothermic Reactions: Release heat to the surroundings (e.g., combustion of methane).
• Endothermic Reactions: Absorb heat from the surroundings (e.g., photosynthesis).

Classification of Reactions

• Acid + Metal: Produces salt and hydrogen gas (e.g., HCl + Mg → MgCl₂ + H₂).
• Acid + Base: Produces salt and water (e.g., HCl + NaOH → NaCl + H₂O).
• Acid + Carbonate: Produces salt, water, and carbon dioxide (e.g., HCl + CaCO₃ → CaCl₂ + H₂O + CO₂).
• Combustion: Reaction of a substance with oxygen, producing carbon dioxide and water.
• Combination/Synthesis: Two or more substances combine to form one product (e.g., A + B → AB).
• Decomposition: A compound breaks down into simpler substances (e.g., AB → A + B).

Explore the fundamental concepts of the periodic table, including its organization into groups and periods. Learn about electron configurations and how they vary among different ions. Test your understanding of metals, nonmetals, and metalloids as well as the principles governing electron arrangement.