AT&T Version 7 Science - Chemistry Comprehension

Introduction

• Focus on the structure of atoms
• Key components of atoms: protons, neutrons, and electrons

Structure of Atoms

• Nucleus: Contains protons (positive charge) and neutrons (no charge)
• Electrons: Negative charge, orbit around the nucleus
• Atomic Charge: Atoms are neutral as the number of protons equals the number of electrons
• Mass of Atoms: Primarily from protons and neutrons
• Atomic Mass Unit (AMU): Protons and neutrons ~1 AMU each; electrons ~0.000549 AMU

Periodic Table

• Atomic Number: Number of protons
• Atomic Mass: Sum of protons and neutrons
• Mnemonic - PAN MAN:
  • PAN: Protons, Atomic number, Number of protons
  • MAN: Mass number, Add, Neutrons

Isotopes

• Atoms of same element with different neutrons
• Example: Carbon isotopes (Carbon-12, Carbon-13, Carbon-14)

Ions

• Definition: Atoms with electrical charge due to gain/loss of electrons
• Cations: Positively charged ions (e.g., Na+)
• Anions: Negatively charged ions (e.g., O2-)

Electron Configuration

• Shells & Subshells: Electrons in different energy levels
  • Shells labeled as K, L, M, N (n=1,2,3,4)
  • Subshells: s, p, d, f with increasing electron capacity
• Orbital shapes: S (sphere), P (dumbbell), D (clover)

Chemical Bonds

• Ionic Bonds: Transfer of electrons (e.g., NaCl)
• Covalent Bonds: Sharing of electrons (e.g., CO2)
• Octet Rule: Atoms prefer 8 electrons in valence shell

States of Matter

• Solids: Definite shape and volume
• Liquids: Indefinite shape, definite volume
• Gases: Indefinite shape and volume

Changes in States of Matter

• Melting: Solid to liquid
• Freezing: Liquid to solid
• Condensation: Gas to liquid
• Evaporation: Liquid to gas
• Sublimation: Solid to gas
• Deposition: Gas to solid

Chemical Reactions

• Types:
  • Synthesis: Two or more reactants form one product
  • Decomposition: One reactant forms two or more products
  • Single Replacement: One element replaces another in a compound
  • Double Replacement: Exchange of ions between two compounds
  • Combustion: Reaction with oxygen, produces CO2 and H2O
• Balancing Equations: Ensure same number of each atom on both sides

Moles and Molar Mass

• Mole: 6.022 x 10^23 particles
• Molar Mass: Sum of atomic masses in a molecule

Reaction Rates

• Influenced by temperature, concentration, surface area, catalysts
• Collision Theory: Reactions occur when particles collide with sufficient energy

Exothermic vs. Endothermic Reactions

• Exothermic: Release energy (e.g., combustion)
• Endothermic: Absorb energy (e.g., photosynthesis)

Equilibrium

• Static vs. Dynamic: Balance in forward/reverse reactions

Water and Solutions

• Cohesion & Adhesion: Water molecules sticking together or to other surfaces
• Solutions: Homogeneous mixtures with solute dissolved in solvent

pH Scale

• Measures acidity/alkalinity (0-14)
• Neutral: pH 7
• Acids: pH < 7
• Bases (Alkalis): pH > 7

Key Concepts for AT&T's Science Portion

• Understanding of basic chemistry, atomic structure, and chemical reactions
• Importance of the periodic table and moles in chemistry
• Significance of water properties and states of matter

Practice Questions

• Questions related to ionic vs covalent bonds, chemical reaction types, pH level interpretations, and more.
• Reinforcement of key concepts through example problems and solutions.

These notes capture key concepts from the lecture on chemistry, focusing on atomic structure, chemical bonds, states of matter, chemical reactions, and the periodic table, along with practical examples and mnemonics to aid understanding.