Chemistry: Atomic Structure and Bonding

Atomic Structure

• Atoms are the fundamental building blocks of matter.
• Atoms consist of a nucleus containing protons and neutrons, with electrons orbiting the nucleus.
• Protons carry a positive charge, neutrons are neutral, and electrons carry a negative charge.
• The number of protons defines the element (atomic number).
• Atoms typically have an equal number of protons and electrons, resulting in a neutral charge.
• Isotopes of an element have the same number of protons but different numbers of neutrons.
• Atomic mass is the sum of protons and neutrons in an atom.
• Electron configuration describes the arrangement of electrons in different energy levels and sublevels around the nucleus.

Chemical Bonding

• Chemical bonds hold atoms together to form molecules or compounds.
• Ionic bonds form between a metal and a nonmetal, where one atom transfers electrons to another, creating positively and negatively charged ions that attract each other.
• Covalent bonds form between nonmetals, where atoms share electrons to achieve a stable electron configuration.
• Metallic bonds form between metal atoms, where electrons are delocalized and free to move throughout the structure.
• Hydrogen bonds are a special type of dipole-dipole attraction between a hydrogen atom bonded to a highly electronegative atom (N, O, or F) and another electronegative atom.

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms to form new substances.
• Reactants are the substances that undergo change, and products are the substances formed as a result of the reaction.
• Chemical equations represent chemical reactions, showing the reactants and products and their relative amounts.
• Balancing chemical equations ensures that the law of conservation of mass is obeyed (equal number of atoms of each element on both sides of the equation).
• Reaction rates describe how fast reactants are consumed and products are formed. Factors influencing reaction rate include temperature, concentration, surface area, and presence of catalysts.
• Types of reactions include synthesis, decomposition, single displacement, double displacement, and combustion.

States of Matter

• Matter exists in three fundamental states: solid, liquid, and gas.
• Solids have a definite shape and volume due to strong intermolecular forces holding particles rigidly in place.
• Liquids have a definite volume but take the shape of their container due to weaker intermolecular forces allowing particles to move past one another.
• Gases have neither a definite shape nor a definite volume; they expand to fill the entire container due to negligible intermolecular forces.
• Plasma is a state of matter consisting of ionized gas, with electrons and ions freely moving.

Periodic Table

• The periodic table is a tabular arrangement of elements, organized by atomic number and recurring chemical properties.
• Elements are grouped into periods (rows) and groups (columns).
• Elements in the same group exhibit similar chemical properties due to having the same number of valence electrons.
• Metals are generally good conductors of heat and electricity, malleable, and ductile.
• Nonmetals are generally poor conductors of heat and electricity, brittle, and often exist as gases or solids with low melting points.
• Metalloids exhibit properties of both metals and nonmetals and are often semiconductors.

Solution Chemistry

• A solution is a homogeneous mixture of two or more substances.
• The solvent is the substance that dissolves the solute.
• Concentration describes the amount of solute dissolved in a given amount of solvent.
• Various units are used to express concentration, including molarity (moles of solute per liter of solution), molality (moles of solute per kilogram of solvent).
• Solubility describes the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature.
• Solutions can be saturated, unsaturated, or supersaturated depending on the amount of solute dissolved.

Acids and Bases

• Acids are substances that release hydrogen ions (H+) when dissolved in water.
• Bases are substances that release hydroxide ions (OH-) when dissolved in water or accept hydrogen ions.
• The pH scale measures the concentration of hydrogen ions in a solution, ranging from 0 (strong acid) to 14 (strong base), with 7 being neutral.
• Strong acids and bases completely dissociate in water, while weak acids and bases partially dissociate.
• Neutralization reactions occur when an acid and base react to form a salt and water.

Thermodynamics

• Thermodynamics studies the relationship between heat, work, and energy changes in chemical and physical processes.
• The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or changed from one form to another.
• The second law of thermodynamics states that the total entropy of an isolated system can only increase over time.
• Enthalpy (H) is a thermodynamic property that measures the heat content of a system.
• Entropy (S) is a thermodynamic property that measures the randomness or disorder of a system.
• Gibbs free energy (G) is a thermodynamic potential that determines the spontaneity of a reaction at constant temperature and pressure.