Chemistry Review

Atoms and Elements All types of matter (solids, liquids and gases) are composed of atoms. A substance that is composed of only one type of atom is called an element. Elements are the simplest form of matter with unique chemical properties. They are charted on the periodic table based on some of their chemical characteristics. There are 24 major elements that have various roles in the body. These include structural, enzymatic, and homeostatic balance. Compounds, like water, are formed by combining the atoms of different elements together. Atoms may create various types of chemical bonds. 3 types of bonds include: Ionic Covalent Hydrogen

Major Elements of the Human Body Oxygen (O): Required for energy production during cellular respiration Carbon (C): Organic back bone for fats, carbohydrates, amino acids and nucleic acids. Hydrogen (H): Vital for energy( ATP) production Nitrogen (N): Most abundant in atmosphere, Characteristic element of protein Phosphorus (P): found in DNA: Blue print for life RNA : Vital for protein production ATP : Cellular energy

The Atom Atoms – identical building blocks for each element Atomic symbol – one- or two-letter chemical short hand for each element Atomic number : # of protons in nucleus periodic table elements arranged by atomic number Atomic weight – equal to the mass of the protons and neutrons Isotope – atoms with same number of protons but a different number of neutrons

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Atomic Structure The nucleus consists of neutrons and protons Neutrons – have no charge and a mass of one atomic mass unit (amu) Protons – have a positive charge and a mass of 1 amu Electrons are found orbiting the nucleus valence electrons are located in the outermost shell interact with other atoms to form bonds Electrons – have a negative charge and 1/2000 the mass of a proton (0 amu)

Chemical Bonds Electron shells, or energy levels, surround the nucleus of an atom. Bonds are formed using the electrons in the outermost energy level Valence shell – outermost energy level containing chemically active electrons Octet rule – except for the first shell which is full with two electrons, atoms interact in a manner to have eight electrons in their valence shell.

Planetary Models of Elements p+ represents protons, no represents neutrons

Chemically Reactive Elements Reactive elements do not have their outermost energy level fully occupied by electrons therefore are able to interact with other elements

Chemically Inert Elements Inert elements have their outermost energy level fully occupied by electrons therefore don’t interact with other elements.

Types of Chemical Bonds Ionic: Covalent Hydrogen

Formation of an Ionic Bond Ionic bonds form between atoms by the transfer of one or more electrons Ionic compounds form crystals instead of individual molecules Example: Na+Cl-(sodium chloride)

Formation of an Ionic Bond A valance electron from Na is transferred to Cl Cl now has 18e and 17p resulting in a – charge Na has 10e and 11P resulting in a + charge.

Ion Formation Ions are charged atoms resulting from the gain or loss of electrons. Anions have gained one or more electrons therefore are negatively charged(-) Cations have lost one or more electrons giving them a positive charge(+) Typically occur between elements on opposite sides of the periodic table.

Electronegativity and Bond Formation Elements on opposite ends of the periodic tables have a greater electronegative gradient. Ionic bonds result. Elements that are closer to each other have smaller electronegative gradient thus form covalent bonds.

Covalent bonds Covalent bonds are formed by the sharing of two or more electrons. Covalent bonds are classified as Polar or Nonpolar. When two atoms with similar electronegativities they share their valance electrons. Nonpolar( neutral charge) bond results. CO2, O2, N2 If there is a larger electronegative gradient between the atoms. a polar covalent bond (charged compound) results. H2O

Nonpolar Bonds Electrons shared equally between atoms produce nonpolar bonds. The negative charged electrons are spaced evenly between the 2 atoms resulting in a neutral charge.

Covalent Bonds

Double Covalent Bonds

Polar Covalent Bonds Uneven sharing of electrons produces polar bonds One atom has a greater electronegativity. This atom will have stronger pull on the shared electrons The shared electrons spend more time closer to the nucleus of electronegative atom. The addition of the shared electrons makes the electronegative atom partially negative charged, while the atom with a lower electronegativity becomes partially positively charged Polar bonds occur between an electronegative atom (mostly O or N) ex. H2O

Inorganic compounds Do not contain carbon Salts : NA+CL– Water, salts, and many acids and bases Minerals such as magnesium and calcium. Salts : NA+CL– contain cations other than H+ and anions other than OH– Are electrolytes; they conduct electrical currents and function in various metabolic reactions. Electrical activity of the nervous system Vital for bone formation

Acid-Base Concentration (pH) pH scale ranges from 0 to 14. Acidic solutions have higher [H+] and a lower pH. Considered proton donors pH less than 7 Alkaline (basic) solutions have lower [H+] and a higher pH Considered proton acceptors pH greater than 7 Neutral solutions have equal H+ and OH– concentrations pH = 7

pH Scale Acids release H+ and are therefore proton donors HCl  H+ + Cl – Bases release OH– and are proton acceptors NaOH  Na+ + OH–

Buffers The body has many mechanisms devoted to resist abrupt and large swings in the pH of body fluids. These systems allow pH to remain relatively constant . Approximately 7.4 (slightly basic) Maintaining a stable pH is critical for creating an environment necessary for metabolic reactions.

Chemical Reactions Chemical reactions in the body act by forming, breaking or rearranging bonds. Chemical equations contain: Relative amounts of reactants (starting chemicals) and products (finishing chemicals) Number and type of reacting substances, and products produced

Synthesis and Decomposition Reactions

Oxidation-Reduction (Redox) Reactions Reactants losing electrons are electron donors and are oxidized Reactants taking up electrons are electron acceptors and become reduced Na + Cl → Na+ + Cl- Na is oxidized and Cl has been reduced LEO THE LION SAYS GER

Forms of Energy Chemical – stored in the bonds of chemical substances Energy from food Electrical – results from the movement of charged particles Household Appliances run on it Mechanical – directly involved in moving matter Machines such as cranes or bull dozers Radiant or electromagnetic – energy traveling in waves visible light, ultraviolet light, and X rays

First Law of Thermodynamics Energy cannot be created or destroyed, but only change form. During each conversion, some of the energy dissipates into the environment as heat. Heat is defined as the measure of the random motion of molecules. the second law states that "energy systems have a tendency to increase their entropy"

Energy The capacity to do work (put matter into motion) Types of energy Kinetic – energy in action. Ball rolling down a hill. Potential – energy of position; stored (inactive) energy. Ball sitting on top of hill.

Fig. 8.2 (TEArt) Energy - the capacity to do work Potential energy Kinetic energy Energy - the capacity to do work kinetic - energy of motion potential - stored energy

Factors Influencing Rate of Chemical Reactions Temperature – chemical reactions proceed quicker at higher temperatures Particle size – the smaller the particle the faster the chemical reaction Concentration – higher reacting particle concentrations produce faster reactions Catalysts – increase the rate of a reaction without being chemically changed Enzymes – biological catalysts