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

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• 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 ReactionsSynthesis 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)

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