Chemistry of Life

Atoms Greek for “indivisible” Smallest possible particle of an element element Made up of Proton (+) Neutron(=)Electron(-) Nucleus= central core of atom made up of proton and neutron Surrounded by electrons Protons Neutrons Electrons Helium atom

Elements Determined by the number of protons in the atom All atoms of that element have the same number of protons Atomic number= number of protons Number of electrons and neutrons is not always consistent. Periodic table is set up to show an element based on it’s atomic mass and the number of electrons in it’s outer shell.

Isotopes An Isotope is an element with a different number of neutrons than protonsAn Isotope is an element with a different number of neutrons than protons Ex: Carbon 12, Carbon 13, Carbon 14Ex: Carbon 12, Carbon 13, Carbon 14 radioactive isotope: an isotope where the nucleus decays over time giving off radiation radioactive isotope: an isotope where the nucleus decays over time giving off radiation

Electrons When an atom is left alone the electrons equal the protonsWhen an atom is left alone the electrons equal the protons Many atoms will lose or gain one electron in bondingMany atoms will lose or gain one electron in bonding Electrons in the highest energy level (valence electrons) determine how it will interact with other atoms.Electrons in the highest energy level (valence electrons) determine how it will interact with other atoms.

Electrons Electron Outermost electron shell (can hold 8 electrons) First electron shell (can hold 2 electrons) Hydrogen (H) Atomic number = 1 Carbon (C) Atomic number = 6

Ionic Bonds A bond that occurs when an atom transfers an electron to another atom. EX: NA-  CL Sodium gives an electron to chlorine NA+ & Cl- NaCl This leads to Ions Ion= an atom that has become electrically charged (+ or-)

Covalent Bond A bond that forms when two atoms share electrons. The number of bonds that can be formed is determined by the number of electrons needed to fill the highest outer level

Molecules A molecule is two or more atoms held together by a covalent bond.

Chemical Reaction The breaking of old and forming of new bonds to make new chemical substances. Reactant: The starting materials Product: The ending materials ReactantsProduct

Water properties

Water All living things are dependent on water Cells are 70% to 95% water Water is the only compound found on earth in all 3 forms Water is one oxygen covalently bonded to two hydrogen's. Although this is a covalent bond the oxygen pulls the shared electrons closer to itself making it more negative and making the hydrogen more positive.

Water properties Oxygen has 6 electrons in it’s highest shell. It wants to have 8 Hydrogen has only one electron in it’s outer shell, it wants 2. They share their electrons allowing for oxygen to gain 2 to make 8 and hydrogen each gets one making it 2. Oxygen has 8 protons in it’s nucleus and this then makes it pull the electrons closer to make the atom neutral. This pull is why water is considered polar and slightly misshapen. The slight polarization of water leads to hydrogen bonds where they are attracted due to polarization not electron sharing or trading.

Water structure

Waters life-supporting properties Cohesion: The tendency of molecules of the same kind to stick to one another. Important in plants because as water evaporates it pulls itself upward in plants. Adhesion: Attraction that occurs between unlike molecules. Important because water sticks to the sides of the plant tubes and helps combat gravity.

Waters life-supporting properties Temperature moderation: Water has a very strong ability to resist change in temperature due to hydrogen bonding between molecules Water allows for temperature regulation of the world by staying cool in the summer and warm in the winter

Waters life-supporting properties Ice: the solid form of water that is lower density than the liquid form. As water freezes the molecules move further apart. Important because it allows animals to continue to live under frozen water instead of being frozen from the bottom up.

Waters life-supporting properties Water has a great ability to dissolve other substances. Water is the universal solvent Solvent: The substance that dissolves another substance Solute: The substance that is being dissolved Solution: A uniform mixture of two or more substances.

Acids, Bases, Buffers, Ph

Ph Scale Water sometimes breaks into ion’s of H+ and OH- Hydrogen ion(+) and Hydroxide ion(-) These ions are what determine whether something is an acid or base. The Ph scale is an exponential scale showing acids and bases. (power of 10)

Ph Scale Scale from 0 to 14 each step is 10x more than the next 0-6 is Acidic 7-8 is neutral 8-14 is Basic

LE 2-15 Acidic solution OH  HH HH HH HH HH HH HH HH HH HH HH HH HH Increasingly ACIDIC (Higher concentration of H  ) Neutral solution OH  HH HH Basic solution NEUTRAL  H        pH scale Lemon juice, gastric juice Grapefruit juice, soft drink Tomato juice Human urine Pure water Human blood Seawater Milk of magnesia Household ammonia Household bleach Oven cleaner Increasingly BASIC (Lower concentration of H  ) OH  HH HH Basic solution Milk of magnesia Household ammonia Household bleach Oven cleaner Increasingly BASIC (Lower concentration of H  )

Acids An acid is any substance that gives off H+ to the solution Ex: lemon juice, stomach acid Acidic solution OH  HH HH HH HH HH HH HH HH Increasingly ACIDIC (Higher concentration of H  ) pH scale

Bases A base is a compound that removes H+ from the solution by giving off OH- to bond with the H+ Ex: Soap, Bleach, Oven cleaner OH  HH HH Basic solution Milk of magnesia Household ammonia Household bleach Oven cleaner Increasingly BASIC (Lower concentration of H  )

Buffer Cells are very sensitive to H+ and OH- ions. Even a slight change in Ph will affect a cell. A buffer will accept H+ ions when they are too high and will donate H+ when they are too low. Blood is a great example of a buffer OH  HH HH HH HH HH Neutral solution NEUTRAL  H        Tomato juice Human urine Pure water Human blood Seawater