chem basics

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shared among a lattice of atoms. 6. Molecules and Compounds: - Molecular compounds consist of nonmetal atoms bonded together. - Ionic compounds consist of positively charged cations and negatively charged anions held together by electrostatic forces. 7. Chemical Reactions: - Chemical reactions are classified as synthesis, decomposition, single replacement, double replacement, or combustion. - Reactivity trends in the periodic table can predict the outcomes of certain reactions. 8. Chemical Equations: - Balancing chemical equations ensures the law of conservation of mass is obeyed. - The coefficients in a balanced equation represent the mole ratio of reactants and products. 9. Law of Conservation of Mass: - This fundamental law states that matter is neither created nor destroyed in a chemical reaction. 10. Acids, Bases, and pH: - Acids can be strong or weak, depending on the degree of ionization in the solution. - Bases can be strong or weak, depending on the degree of dissociation in the solution. - The pH scale is logarithmic, meaning each unit change represents a tenfold difference in hydrogen ion concentration. 11. Solutions and Concentration: - The concentration of a solution can be expressed in various units, such as molarity (moles per liter) or molality (moles per kilogram). - Colligative properties (e.g., boiling point elevation, freezing point depression) depend on the number of solute particles in solution. 12. States of Matter and Changes: - Sublimation is the direct transition from a solid to a gas without passing through the liquid state. - Deposition is the reverse process, where a gas transforms directly into a solid. 13. Energy and Chemical Reactions: - Activation energy is the energy required to start a chemical reaction. - Catalysts lower the activation energy, increasing the reaction rate without being consumed. 14. The Periodic Table: - Elements are grouped into periods (rows) and families/groups (columns) based on similar properties. - Main group elements are in groups 1, 2, and 13-18, while transition metals are in the middle of the table. 15. Atomic Mass and Molar Mass: - Atomic mass is expressed in unified atomic mass units (u) and is relative to the mass of an atom of carbon-12. - Molar mass is expressed in grams per mole (g/mol) and is used in stoichiometric calculations. 16. Chemical Formulas: - Empirical formulas show the simplest whole-number ratio of atoms in a compound. - Molecular formulas provide the actual number of atoms of each element in a molecule. 17. The Avogadro Constant and Mole Concept: - One mole of any substance contains Avogadro's number (6.022 x 10^23) of particles, which can be atoms, ions, or molecules. 18. Stoichiometry: - Stoichiometric calculations involve mole-mole ratios, mass-mass ratios, and mass-volume relationships in chemical reactions. 19. Gas Laws: - Boyle's law describes the inverse relationship between pressure and volume at a constant temperature. - Charles's law describes the direct relationship between volume and temperature at constant pressure. - Avogadro's law states that equal volumes of gases at the same temperature and pressure contain the same number of molecules. 20. Nuclear Chemistry: - Nuclear reactions involve changes in the nucleus of atoms, leading to the formation different isotopes and the release of energy. - Types of nuclear decay include alpha decay, beta decay, and gamma decay. 21. Periodic Trends: - Periodic trends include atomic radius, ionization energy, electron affinity, and electronegativity. - These trends help predict the behavior and reactivity of elements in the periodic table. 22. Organic Chemistry Basics: - Organic compounds contain carbon and hydrogen, often with other elements like oxygen, nitrogen, or halogens. - Functional groups are specific arrangements of atoms that determine the chemical properties of organic compounds. 23. Redox Reactions: - Redox reactions involve the transfer of electrons between reactants. - Oxidation is the loss of electrons, while reduction is the gain of electrons. 24. Equilibrium: - Chemical equilibrium occurs when the forward and reverse reactions proceed at the same rate, and concentrations stabilize. - Le Chatelier's principle predicts the effects of changes in temperature, pressure, and concentration on the equilibrium position. 25. Thermodynamics: - Thermodynamics deals with the study of energy changes during chemical reactions and phase transitions. - The first law of thermodynamics states that energy is conserved in a closed system. - The second law of thermodynamics states that the entropy of an isolated system tends to increase over time.