Chemistry Chapter: Atomic Structure & Bonding

Basic Concepts:
- Atoms are the smallest units of matter.
- Composed of protons, neutrons (nucleus), and electrons (orbitals).
Subatomic Particles:
- Protons: Positively charged, located in the nucleus, defines the atomic number.
- Neutrons: No charge, also in the nucleus, contributes to atomic mass.
- Electrons: Negatively charged, orbit the nucleus in energy levels.
Atomic Number & Mass:
- Atomic number (Z): Number of protons in an atom.
- Mass number (A): Total number of protons and neutrons.
Isotopes:
- Atoms with the same atomic number but different mass numbers due to varying neutrons.

Types of Bonds:
- Ionic Bonds: Formed by the transfer of electrons from one atom to another (e.g., NaCl).
- Covalent Bonds: Formed by the sharing of electrons between atoms (e.g., H2O).
- Metallic Bonds: Involves a ‘sea of electrons’ shared among metal atoms.
Molecular Shapes:
- Determined by the arrangement of atoms in a molecule (VSEPR theory).
Polarity:
- Polar molecules have unequal sharing of electrons (e.g., HCl).
- Nonpolar molecules have equal sharing (e.g., O2).

Organization:
- Arranged by increasing atomic number.
- Rows are called periods; columns are groups or families.
Trends:
- Atomic Radius: Decreases across a period, increases down a group.
- Electronegativity: Increases across a period, decreases down a group.
- Ionization Energy: Energy required to remove an electron; increases across a period, decreases down a group.
Categories of Elements:
- Metals: Good conductors, malleable, ductile.
- Nonmetals: Poor conductors, brittle, varied states at room temperature.
- Metalloids: Properties of both metals and nonmetals.

Types of Reactions:
- Synthesis: A + B → AB.
- Decomposition: AB → A + B.
- Single Replacement: A + BC → AC + B.
- Double Replacement: AB + CD → AD + CB.
- Combustion: Hydrocarbon + O2 → CO2 + H2O.
Law of Conservation of Mass:
- Mass is neither created nor destroyed in a chemical reaction.
Balancing Equations:
- Ensure the number of atoms for each element is the same on both sides of the equation.

Chemical Symbols:
- One or two-letter abbreviations for elements (e.g., H for Hydrogen, O for Oxygen).
Chemical Formulas:
- Represents compounds (e.g., H2O for water, CO2 for carbon dioxide).
Equations:
- Expresses chemical reactions; reactants on the left, products on the right.
Subscripts and Coefficients:
- Subscripts indicate the number of atoms (e.g., C6H12O6).
- Coefficients indicate the number of molecules (e.g., 2H2 + O2 → 2H2O).

Chemical Properties:
- Chemical formula: H2O.
- Polar molecule with a bent shape due to the arrangement of hydrogen atoms.
Properties:
- High specific heat capacity: Helps regulate temperature.
- Universal solvent: Can dissolve many substances.
- Cohesion and adhesion: Leads to surface tension and capillary action.
States of Water:
- Solid (ice), liquid (water), gas (water vapor).
- Phase changes involve energy changes: melting, freezing, evaporation, condensation.
Importance:
- Essential for all living organisms.
- Involved in biochemical reactions (e.g., photosynthesis, respiration).

Atoms are the basic units of matter, consisting of protons, neutrons, and electrons.
Protons are positively charged particles found in the nucleus and define the atomic number.
Neutrons are neutral particles also located in the nucleus, contributing to the atomic mass.
Electrons are negatively charged and occupy orbitals around the nucleus in defined energy levels.
The atomic number (Z) reflects the number of protons, while the mass number (A) is the total of protons and neutrons.
Isotopes are variants of elements with the same atomic number but different mass numbers, caused by varying numbers of neutrons.

Ionic bonds arise from the transfer of electrons, exemplified by sodium chloride (NaCl).
Covalent bonds form through the sharing of electrons, as seen in water (H2O).
Metallic bonds consist of a 'sea of electrons' that flow freely among metal atoms.
Molecular shapes are determined by the arrangement of atoms, analyzed through VSEPR theory.
Polar molecules, like hydrochloric acid (HCl), exhibit unequal sharing of electrons, while nonpolar molecules, such as oxygen (O2), have equal sharing.

Elements are arranged in the periodic table by increasing atomic number, with rows called periods and columns known as groups or families.
Atomic radius decreases across a period and increases down a group, demonstrating periodic trends.
Electronegativity increases across a period but decreases down a group, influencing chemical bonding.
Ionization energy, the energy required to remove an electron, also increases across a period and decreases down a group.
Metals are good conductors and are malleable and ductile, while nonmetals are poor conductors and tend to be brittle. Metalloids exhibit properties of both categories.

Types of chemical reactions include synthesis, decomposition, single replacement, double replacement, and combustion.
The Law of Conservation of Mass states that mass is conserved in a chemical reaction, meaning it cannot be created or destroyed.
Balancing chemical equations ensures that the same number of each type of atom exists on both sides of the reaction.

Chemical symbols are shorthand representations of elements, such as H for hydrogen and O for oxygen.
Chemical formulas denote compounds, like H2O for water and CO2 for carbon dioxide.
Chemical equations illustrate reactions, positioning reactants on the left and products on the right.
Subscripts in formulas represent the number of atoms in a molecule, while coefficients indicate the number of molecules participating in the reaction.

Water's chemical formula is H2O, and it is a polar molecule with a bent molecular geometry due to its hydrogen atom arrangement.
Key properties of water include a high specific heat capacity, which helps stabilize temperatures, and its status as a universal solvent that dissolves a wide range of substances.
Water demonstrates cohesion and adhesion, resulting in surface tension and capillary action.
It exists in three states: solid (ice), liquid (water), and gas (water vapor), with phase changes involving energy transformations.
Water is vital for all living organisms, playing critical roles in biochemical processes like photosynthesis and respiration.