High School Chemistry Unit Review and Study Guide

Significant Figures:
- Rules for identifying significant figures involve counting non-zero digits and specific zero placements (e.g., $0.0007$ has 1 significant figure, $5050$ has 3, and $387$ has 3).
- Calculation Rules:
- Addition/Subtraction: Result matches the value with the fewest decimal places (e.g., $6.2 + 4.114 = 10.3$ , as $6.2$ has one decimal place).
- Multiplication/Division: Result matches the value with the fewest significant figures (e.g., $1000 \text{ (1 significant figure)} \text{ divided by } 8.2 \text{ (2 significant figures)} = 100$ ).
Scientific Notation:
- Conversion of values into powers of 10 is utilized for easier representation of large or small numbers (e.g., $6.8 \times 10^4$ indicates $68000$ ).
Data Types:
- Quantitative: Numerical measurements (e.g., $4.3 \text{ g}$ indicates mass, $110 \text{ kPa}$ indicates pressure, pH increased from $4.5$ to $5.2$ ).
- Qualitative: Descriptive observations (e.g., color is yellow, bubbles formed during reaction, strong odor noticed in a sample).

Phase Changes:
- Represents transitions between states of matter: melting, vaporization, condensation, freezing, sublimation, and deposition, with attention to energy changes.
Heating/Cooling Curves:
- Observations of energy changes include Kinetic Energy decreasing versus Potential Energy changing during phase transitions, illustrating the principles of thermal energy transfer.
Classification of Matter:
- Pure Substances:
- Elements: Basic substances (e.g., $H_2$ gas).
- Compounds: Chemical combinations of elements (e.g., Rust/Iron oxide, $CH_4$ , which has distinct properties).
- Mixtures:
- Homogeneous: Uniform composition (e.g., Saltwater, Air), where components are not easily distinguishable.
- Heterogeneous: Non-uniform composition (e.g., Food dye in water), where individual components can be identified.
Separation Techniques:
- Distillation: Separates liquids based on different boiling points (e.g., separating ethanol from water).
- Filtration: Separates solids from liquids (e.g., sand from water).
- Chromatography: Physical method for separating mixtures based on movement through a medium (e.g., ink separation).
- Centrifuge: Separation based on density, with denser materials settling faster than lighter ones.

Atomic Scientists:
- Key contributors include Democritus, Dalton, Thomson (Plum Pudding model), Rutherford (nuclear model), Bohr (energy levels), Schrodinger (quantum model), and Chadwick (discovery of the neutron).
Atomic Structure:
- Defined by atomic number ( $Z$ ), mass number ( $A$ ), and net charge of the atom.
Isotopes:
- Different forms of the same element that contain varying numbers of neutrons (e.g., $^{50}V$ has 28 neutrons, $^{51}V$ has 29 neutrons).
Periodic Trends:
- Atomic Radius:
- Decreases across a period due to increased nuclear charge, which pulls electrons closer to the nucleus; increases down a group due to additional electron shells.
- Ionization Energy and Electronegativity:
- Generally increase across a period and decrease down a group, impacting the reactivity and bonding behavior of elements.
- Metallic Character:
- Decreases across a period as elements become more non-metallic.
- Alkali Metal Reactivity:
- Increases down Group 1, with alkali metals becoming more reactive as their atomic size and shielding effect increases.

Configuration:
- Notations describe electron placement in atoms (e.g., $Li: 1s^2 2s^1$ ; $P^{3-}: 1s^2 2s^2 2p^6 3s^2 3p^6$ illustrate the arrangement of electrons across shells).
Orbits:
- Each d-sublevel can hold up to 10 electrons across 5 orbitals, influencing reactivity and bonding properties.
Bonding Types:
- Ionic: Involves metal to nonmetal transfer of electrons, resulting in high melting points and electrical conductivity in solution.
- Covalent: Nonmetal to nonmetal sharing of electrons leads to varied bond strengths and molecular formations.
- Metallic: Characterized by a