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Chapter 2: Basic Chemistry
Transcript of Chapter 2: Basic Chemistry
Basic Chemistry Matter anything that takes up space and has mass:
made up of elements Mass the amount of matter in an object Element a substance that cannot be broken down into other substances by chemical reactions C H O N The four elements essential to life Trace
Elements elements that are required by an organism, but only in minute amounts. Ex: Iron and Iodine Compounds a substance of consisting of two or more elements in a fixed ratio; has characteristics different from those of its elements
Ex.Table salt (NaCl)- Na & Cl in a 1:1 ratio Atoms smallest unit of matter that retains the properties of an element Consists of subatomic
particles -Neutrons: No charge -Protons: Positive Charge -Electrons: Negative charge Isotopes two atoms of the same element that differ in the number of neutrons radioactive isotopes unstable isotopes that decay spontaneously, emitting particles and energy have several applications in biologial research -can be used to trace metabolic processes -are also used to diagnose and treat medical disorders (cancer) Energy ability to do work Potential energy: the energy that matter possesses because of its location or structure Electrons have potential energy because of ther position relative to the nucleus:
-1st shell: lowest potential energy
-Electrons in outer shells have more p. energy chemical behavior of an atom depends mostly upon the # of electrons in its outermost shell, called the valence shell: electrons are known as valence electrons atoms with the same # of valence electrons have similar chemical behavior: atoms are chemically reactive because they have incomplete valence sheels it is the unpaired electrons that are involved when atoms interact to complete their valence shells; creating bonds between atoms Covalent Bonding sharing of a pair of valence electrons by 2 atoms 2 or more atoms held together by covalent bonds consitute a molecule Structural formula:
represents both atoms
and bonding Molecular Formula:
indicates the number and types of atoms present in a single molecule Single Bond: a pair of shared electrons Double Bond: when 2 or more atoms are sharing 2 pairs of electrons Triple Bond: when 2 or more atoms are sharing 3 pairs of valence electrons covalent bonds can form between atoms of the same element or atoms of different elements covalent compound: a combination of two or more different elements nonpolar covalent bond: when electrons in a covalent bond are shared equally by atoms -bonds between 2 atoms of the same element are always nonpolar -bonds between 2 atoms that have a similiar electronegativity is also nonpolar electronegativity: the attraction of an atom for the shared electrons of a covalent bond Ionic Bonding if 2 atoms are unequal in their attraction for valence electrons that one atom strips an electron completely from the other after the transfer, both atoms are no longer neutral, but have charges called ions -atom with (+) are CATIONS
-atoms with (-) are ANIONS
-held together because of their opposite charges Weak
Chemical Bonds Hydrogen Bonding: when a H atom covalently bonded to 1 electronegative atom is also attracted to another electronegative atom Van der Waals Interactions: weak interactions that occur only when atoms & molecles are very close together Molecular Shape/ Function Polar Covalent Bond:
when 2 atoms that differ in electronegativity; they do not share the electron pair equally 3-D shape of a molecule is crucial in biology it determines how biological molecules recognize & respond to one another Molecules with 2 atoms
are always linear More than 2 atoms has a more complex structure Shape depends on the positions of the electron orbitals that are shared Chemical Reactions making & breaking of chemical bonds, leading to changes in the composition of matter Chemical Equilibrium the point at which the reactions offset one another (the forward & reverse reactions occur at the same time also called dynamic equilibrium: reactions are still going on, but with no net effect on the concentration of reactants & products C H O N