Atomic Structure Basics

Atomic Structure

• Atomic Model: The modern atomic model consists of:
  • Protons (positive charge) in the nucleus
  • Neutrons (no charge) in the nucleus
  • Electrons (negative charge) in energy levels around the nucleus
• Electron Configuration:
  • Electron shells (energy levels) have a maximum number of electrons
  • The first shell can hold up to 2 electrons, the second shell up to 8, and so on
  • Electron configuration notation: 1s2 2s2 2p6 (example)
• Subatomic Particles:
  • Protons: positively charged, mass of 1 amu (atomic mass unit)
  • Neutrons: no charge, mass of 1 amu
  • Electrons: negatively charged, negligible mass

Chemical Bonding

• Types of Chemical Bonds:
  1. Ionic Bonds: Formed by the transfer of electrons between atoms
     • Cations (positively charged) and anions (negatively charged) attract each other
  2. Covalent Bonds: Formed by the sharing of electrons between atoms
     • Polar covalent bonds: unequal sharing of electrons, resulting in a partial charge
     • Nonpolar covalent bonds: equal sharing of electrons
  3. Hydrogen Bonds: Weak bonds between hydrogen and highly electronegative atoms (F, O, N)
• Bond Properties:
  • Bond length: distance between the nuclei of two bonded atoms
  • Bond energy: energy required to break a bond
  • Bond polarity: difference in electronegativity between bonded atoms

States of Matter

• Solid:
  • Particles are closely packed and vibrate in place
  • Has a fixed shape and volume
• Liquid:
  • Particles are close together but able to move past each other
  • Has a fixed volume but takes the shape of its container
• Gas:
  • Particles are widely spaced and move freely
  • Has neither a fixed shape nor volume
• Phase Changes:
  • Melting: solid to liquid
  • Freezing: liquid to solid
  • Vaporization: liquid to gas
  • Condensation: gas to liquid

Stoichiometry

• Mole: A unit of measurement, 6.022 x 10^23 particles (atoms, molecules, ions)
• Molar Mass: The mass of one mole of a substance, in grams
• Empirical Formula: The simplest whole-number ratio of atoms in a compound
• Molecular Formula: The actual number of atoms in a molecule
• Stoichiometric Calculations:
  • Moles of reactants to moles of products
  • Mass of reactants to mass of products
  • Limiting reagent: the reactant that determines the amount of product formed

Atomic Structure

• Atomic model consists of protons, neutrons, and electrons
• Protons have a positive charge and neutrons have no charge, both are found in the nucleus
• Electrons have a negative charge and are found in energy levels around the nucleus
• Electron shells have a maximum number of electrons, with the first shell holding up to 2 electrons, the second shell up to 8, and so on
• Electron configuration notation is used to describe the arrangement of electrons in an atom, for example, 1s2 2s2 2p6

Subatomic Particles

• Protons have a mass of 1 amu (atomic mass unit) and a positive charge
• Neutrons have a mass of 1 amu and no charge
• Electrons have a negligible mass and a negative charge

Chemical Bonding

• Chemical bonds are formed between atoms through the transfer or sharing of electrons
• Ionic bonds are formed by the transfer of electrons, resulting in positively charged cations and negatively charged anions that attract each other
• Covalent bonds are formed by the sharing of electrons between atoms, resulting in a molecule
• Polar covalent bonds involve unequal sharing of electrons, resulting in a partial charge, while nonpolar covalent bonds involve equal sharing of electrons
• Hydrogen bonds are weak bonds between hydrogen and highly electronegative atoms such as fluorine, oxygen, and nitrogen

Bond Properties

• Bond length is the distance between the nuclei of two bonded atoms
• Bond energy is the energy required to break a bond
• Bond polarity is the difference in electronegativity between bonded atoms

States of Matter

• In a solid, particles are closely packed and vibrate in place, having a fixed shape and volume
• In a liquid, particles are close together but able to move past each other, having a fixed volume but taking the shape of its container
• In a gas, particles are widely spaced and move freely, having neither a fixed shape nor volume
• Phase changes occur when a substance changes from one state of matter to another, such as melting, freezing, vaporization, and condensation

Stoichiometry

• A mole is a unit of measurement, equal to 6.022 x 10^23 particles (atoms, molecules, or ions)
• Molar mass is the mass of one mole of a substance, in grams
• The empirical formula is the simplest whole-number ratio of atoms in a compound
• The molecular formula is the actual number of atoms in a molecule
• Stoichiometric calculations involve the mole ratio of reactants to products, and the mass ratio of reactants to products
• The limiting reagent is the reactant that determines the amount of product formed