Chemical Bonds and Reactions (Lecture)

mixtures

Formed by physically combined matter

Colloid

two or more components, small, evenly distributed particles, will not settle out (ex: gelatin)

solution

two or more components; extremely small, evenly distributed particles'; will not settle out

solute

substance dissolved

solvent

substance that dissolves solute (usually water)

suspension

two or more components, large, unevenly distributed particles, will settle out when left undisturbed (ex: blood, rbc and wbc in plasma)

chemical bonds

matter combined chemically to form energy relationships between electrons of reacting atoms

chemical bonds

2 or more atoms held together by a bond, interactions between electrons

molecules

2 or more atoms of the same element

compound

2 or more atoms of different elements

electrons in valence shell

have most potential energy, chemically reactive

Octet rule (rule of eights)

except for the first shell (full with two electrons) atoms interact to have eight electrons in their valence shell

Noble Gases

Elements on the furthest right column of the periodic table

Stable and Unreactive

when the outermost energy level (valence shell) has 8 electrons

Unstable and Reactive

valence shell not full, tend to gain, lose, or share electrons (form bonds) with other atoms to achieve stability

types of chemical bonds

ionic, covalent, hydrogen

ionic bond

results when there is an attraction of opposite charges, usually between a metal and nonmetal (ex: NaCl, sodium gains stability by losing one electron, and chlorine becomes stable by gaining one electron, after electron transfer, the oppositely charged ions attract each other)

anion

negative charge, atom that gained one or more electrons

cation

positive charge, atom that has lost one or more electrons

covalent bonds

formed by sharing of two or more valence shell electrons, allows each atom to fill its valence shell at least part of the time, between two nonmetals, electrons are shared; bond results from pull of electrons by each atom

nonpolar covalent bonds

electrons shared equally, produces electrically balance molecules (ex: CO2)

3 situations where nonpolar molecules occur

atoms sharing electrons are same element, arrangement of atoms makes one atom unable to pull more strongly than other atom (CO2). bond is between carbon and hydrogen

Polar Covalent Bonds

electrons shared unequally, produces electrically charged, polar molecules (ex: H2O)

electronegative

small atoms with six or seven valence shell electrons, strong electron-attracting ability

electropositive

most atoms with one or two valence shell electrons

stronger pull

more electrons in valence shell

dipoles

water molecules, have two poles of charge

hydrogen bonds

attractive force between electropositive hydrogen of one molecule and an electronegative atom of another molecule, not true bond, very weak, common between dipoles such as water, also act as intramolecular bonds, holding a large molecule in a three-dimensional shape, allows for surface tension

chemical reactions

occur when chemical bonds are formed, rearranged, or broken, represented as chemical equations using molecular formulas

components of a chemical equation

reactants, products, relative proportion of each reactant and product when balanced

reactants

number and kind of reacting substances, left side of the arrow in an equation

product

substance created, right side of the arrow in an equation

chemical equilibrium

occurs if neither a forward nor reverse reaction is dominant

biological reactions

essentially irreversible due to energy requirements and removal of products

energy

capacity to do work or put matter into motion or fuel chemical reactions; two general forms: kinetic and potential

Potential energy

stored; can be released later to do work

Kinetic energy

potential energy has been released or set in motion to perform work; all atoms have this; faster movement=greater energy

Three forms of energy in human body

Chemical, Electrical, Mechanical

chemical energy

in bonds between atoms; drives nearly all chemical processes

electrical energy

generated by movement of charged particles or ions

mechanical energy

energy directly transferred from one object to another

exergonic

energy is released when breaking bonds (catabolic reactions)

endergonic

energy is required to form a bond (anabolic reactions)

Types of Chemical Reactions

Synthesis/Anabolic, Decomposition/Catabolic , exchange

Synthesis/Anabolic

atoms or molecule s combine to form larger, more complex molecule, always involves bond formation; requires energy input, endergonic

Synthesis

smaller particles are bonded together to form larger, more complex molecules

Decomposition/Catabolic

molecule is broken down into smaller molecules or its constituent atoms, reverse of synthesis reactions, involved breaking of bonds; releases energy, exergonic

Exchange/Displacement

involves both synthesis and decomposition one or more atoms from reactants are exchanged for one another, bonds are both made and broken

oxidation- reduction reactions

special kind of exchange reaction; electrons and energy are exchanged instead of atoms, electrons are exchanged between reactants

electron donors

lose electrons and are oxidized

electron acceptors

gain electrons and become reduced