Concept Notes on Chemistry PDF

**CONCEPT NOTES:** - **[Ionic Bond]** -- bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other**. (metal and nonmetal)** - **[Ionization energy (IE)]** -- is the amount of energy...

**CONCEPT NOTES:** - **[Ionic Bond]** -- bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other**. (metal and nonmetal)** - **[Ionization energy (IE)]** -- is the amount of energy it takes to detach one electron from a neutral atom. - **[Ion]** -- is a charged atom or molecule. It is charged because the number of electrons does not equal the number of protons in the atom or molecule. - **[Octet Rule]** (8 electrons on outer shell) states that when atoms of elements combine to form compounds, they tend to lose, gain, or share electrons to achieve the same electron arrangement as the noble gas nearest them in the periodic table. - **[Lewis Dot Symbol]** consists of the symbol of an element and one dot for each valence electron in an atom of the element. - **[A covalent bond]** two electrons are shared equally between the two atoms**. (both nonmetal elements**) - **[In the Lewis structure]**, shared electrons that form a bond is represented by a line or a pair of dots; lone pairs are represented by dots above the atom. - Exemptions to Octet Rule: a. Incomplete Octet b. Odd number of electrons c. Expanded Octet - **[PHASE]** is a homogeneous part of a system in contact with other part of the system, but separated by well-defined boundaries. - **[CONDENSED PHASES]** are solids and liquids. - **[INTRAMOLECULAR FORCES]** hold atoms together in a molecule. (within) - **[INTERMOLECULAR FORCES]** (between) are attractive forces that act between molecules or particles in the solid or liquid states. These attractive forces are much weaker than bonding forces. - **[1. London Dispersion forces (weakest)]** -- result from temporary dipole moments induced in ordinarily nonpolar molecules. As electrons move around the nucleus, an uneven distribution causes momentary charge separations. Slightly positive sides of a molecule are attracted to the slightly negative sides of the adjacent molecule. - **[2. Dipole-dipole forces]** -- are attractive forces between polar molecules (molecules that possess dipole moments). In polar molecules, the electrons are unevenly distributed because some elements are more electronegative than others. - **[3. Hydrogen Bond]= special type of bond of dipole**-dipole forces. Hydrogen is bonded to N,O,F (POLAR MOLECULES SAME WITH DIPOLE-DIPOLE) - **[4. Ion-dipole forces]** -- polar molecules are attracted to ions. The positive pole is attracted to a negative ion (anion), while the negative pole is attracted to a positive ion (cation). - 5.Ion- Ion interactions= ( both ions are attracted to one another) - **[Surface Tension --]** the measure of the elastic force in the surface of a liquid. It is the amount of energy required to stretch or increase the surface of a liquid by a unit area. - **[Capillary Action]** -- is the tendency of a liquid to rise in narrow tubes or to be drawn into small openings. **[Cohesion]** is the intermolecular attraction between like molecules (liquid molecules). **[Adhesion]** is an attraction between unlike molecules (such as those in water and in the particles that make up the glass tube). - **[Viscosity --]** a measure of a fluid's resistance to flow. - Liquids that have strong intermolecular forces have higher viscosities than those that have weak intermolecular forces. - Viscosity decreases as temperature increases. **[(vice versa)]** - **[Vapor pressure of a liquid]** -- the equilibrium pressure of a vapor above its liquid; that is, the pressure exerted by the vapor above the surface of the liquid in a closed container. - **[equilibrium vapor pressure]** is the maximum vapor pressure of a liquid at a given temperature and that it is constant at a constant temperature. It increases with temperature. - **The stronger the intermolecular forces of attraction, the lower the vapor pressure of a liquid.** - **[Molar heat of vaporization (ΔHvap)]** -- the energy required to vaporize 1 mole of a liquid at a given temperature. - If the intermolecular attraction is strong, it takes a lot of energy to free the molecules from the liquid phase and the heat of vaporization will be high. - The **[boiling point]** is related to molar heat of vaporization: the higher the molar heat of vaporization, the higher the boiling point. ***[TYPES OF SOLID CRYSTALS ( CRYSTALLINE AND AMORPHOUS)]*** - **[Crystal or crystalline solid]** -- is a solid material whose components, such as atoms, molecules or ions, are arranged in a highly ordered microscopic structure. - Arranged in **[fixed geometric patterns or lattices]**. The ordered arrangement of their units maximizes the space they occupy and are essentially incompressible. - **[Amorphous Solids =]** Have a **[random orientation of particles]**. They are considered super-cooled liquids where molecules are arranged in a random manner similar to the liquid state. ***[TYPES OF CRYSTALS]*** - **[Metallic Crystals]** -- are made of atoms that readily lose electrons to form cations, but no atoms in the crystal would readily gain electrons. The crystal is held together by electrostatic interactions between the cations and delocalized electron. These interactions are called metallic bonds. - **[Ionic crystal --]** a solid that consists of positively and negatively charged ions held together by electrostatic forces. - **[Molecular Crystals --]** are made of atoms. The atoms or molecules are held together by a mix of hydrogen bonding/dipole-dipole or dispersion forces, and these are the attractive forces that are broken when the crystal melts. - **[Covalent Network Crystals] --** are made of atoms in which each atom is covalently bonded to its nearest neighbors. [ ] - **[Phase Changes]** are transformation of matter from one physical state to another. - **[Phase Diagram]** is a graphical representation of the physical states of a substance under different conditions of temperature and pressure. **Features of a Phase Diagram** - **THREE AREAS** *The three areas are marked [**solid, liquid, and vapor**.]* - **Three Lines (Curves)** *The green line divides the solid and liquid phases and represents melting (solid to liquid) and freezing (liquid to solid) points.* *The blue line divide the liquid and gas phases and represent vaporization (liquid to gas) and condensation (gas to liquid) points.* - **The Two Important Points** = ***triple point and critical point*** - *[The **triple point**] is the combination of pressure and temperature at which all three phases of matter are at equilibrium. It is the point on a phase diagram at which the three states of matter coexist.* - *The **[critical point]** terminates the liquid/gas phase line. It is the set of temperature and pressure on a phase diagram where the liquid and gaseous phase of a substance merges together into single phase. Beyond the temperature of the critical point, the merged single phase is known as a **supercritical fluid**.*  - **[Thermochemistry]** -- is the study of heat and energy changes that accompany physical and chemical processes. - **[ Enthalpy]** is a measure of heat flow at a constant pressure, and its unit **[is joule (J) or kilojoule (kJ).]** Heat of reaction or change in **[enthalpy]** is expressed in **[kJ/mole]** - **[Exothermic change]** **[energy is released]** to the surroundings when a change occurs. The heat released by **[an exothermic reaction]** often results to an increase in the temperature of the reaction mixture and the reaction vessel, and possibly the air surrounding the vessel. Burning of fuels is an example of exothermic reaction. - **[Endothermic change]** = **[absorption]** of energy from the surroundings. **[When an endothermic change occurs]**, the temperature of the reaction mixture decreases since part of the kinetic energies of particles in the surroundings is absorbed for use in the reaction. Cooking of food is the best example of this type of reaction.