Ch+2+Atoms%2C+Molecules%2C+and+Ions

Atoms, Molecules, and Ions

Law of Conservation of Mass

• Definition: The total mass of substances is conserved in a chemical process; it remains unchanged before and after the process.

• Example:

  • Before: 63.5 g copper + 320 g oxygen

  • After: 79.5 g copper (II) oxide + ? g oxygen

  • Total mass before = Total mass after = 383.5 g (both sides equal)

Modern Atomic Theory

• Structure of Atom:

  • Nucleus:

    • Protons: Positive charge (+), relative mass = 1

    • Neutrons: Neutral charge, relative mass = 1

  • Electron Cloud:

    • Electrons: Negative charge (-), negligible mass (relative mass = 0)

Periodic Table of Elements

• Organization:

  • Groups (vertical)

  • Periods (horizontal)

• Example Elements:

  • Group 1: Hydrogen (H), Lithium (Li), Sodium (Na)

  • Group 2: Beryllium (Be), Magnesium (Mg)

  • Transition Metals: Iron (Fe), Copper (Cu), Zinc (Zn)

Isotopes and Ions

• Isotopes:

  • Definition: Atoms of the same element with different numbers of neutrons.

  • Example: Helium-4 has 2 protons and 2 neutrons.

• Ions:

  • Definition: Charged particles due to loss/gain of electrons.

  • Cation: Positive ion (loss of electrons)

  • Anion: Negative ion (gain of electrons)

Ionic and Covalent Bonds

• Ionic Bonds:

  • Formation: Between metals and nonmetals

  • Nature: Result from the electrostatic attraction between oppositely charged ions (e.g., NaCl: Na+ and Cl-)

• Covalent Bonds:

  • Formation: Within nonmetal atoms, sharing electrons between nuclei.

  • Example: Oxygen molecules (O2) share electrons to achieve stability.

Metal, Metalloids, and Non-Metals

• Categories:

  • Metals

    • Properties: Shiny, good conductors of heat/electricity, malleable, solid at room temperature (except Hg)

  • Non-Metals

    • Properties: Dull, insulators, can be solid, liquid, or gas, brittle when solid

  • Metalloids

    • Properties: Exhibit properties of both metals and nonmetals

Chemical Properties of Nonmetals, Metals, and Metalloids

• Nonmetals: Typically have high ionization energies and electronegativities, form anions

• Metals: Tend to lose electrons forming cations, have low ionization energies

• Metalloids: Characteristics between metals and nonmetals, can behave as either depending on conditions (semiconductors)

Bonds and Their Types

• Ionic Bonds:

  • Result from oppositely charged ions, transfer of electrons from metal to nonmetal.

• Covalent Bonds:

  • Occur when sharing of electrons takes place among nonmetals.

Bonding and Molecular Structure

• Electrostatic Forces: Drives attraction/repulsion forces in bonded atoms.

• Geometric Shapes: Influence the properties and reactivity of compounds.

Ionic Compounds and Prefixes

• Nomenclature:

  • Names of ionic compounds typically end in -ide for simple ions.

  • Polyatomic ions have unique names (e.g., sulfate, nitrate).

Reminder about Ionic Compounds

• Write formulas based on the lowest whole-number ratio of ions.

• Charges of cations and anions determine the compound’s formula.

Acids and Bases Concept

• Classes:

  • Binary Acids: Contain hydrogen and one other non-metal

  • Oxyacids: Contain hydrogen, oxygen, and another element

  • Naming acid depends on presence of oxygen and number of oxygens (e.g., HCl is hydrochloric acid, HNO3 is nitric acid)

Empirical vs. Molecular Formula

• Empirical Formula: Simplest whole-number ratio of elements in a compound.

• Molecular Formula: Actual number of each type of atom in a molecule.

• Example:

  • Hydrogen Peroxide: Molecular formula is H2O2, empirical formula is HO.

Notable Elements**

• Hydrogen (H), Nitrogen (N), Oxygen (O), Carbon (C)

• Polyatomic Cations: Ammonium (NH4+), Hydronium (H3O+)

• Polyatomic Anions: Nitrate (NO3-), Phosphate (PO4^3-), etc.