Basic Chemistry

Chemical Elements Matter – anything that takes up space and has mass –Composed of elements Element – substance that cannot be broken down to simpler substances with different properties All living and nonliving things are matter composed of elements

The Atom – John Dalton Smallest part of an element that displays the properties of the element Subatomic particles –Neutron – neutral charge –Proton –positive charge –Electron – neg. charge

The atom Atomic number = # of protons (usually # of electrons if atom is neutral) Atomic mass = protons and neutrons # of neutrons = Atomic mass – P+

Periodic Table Dimitri Mendeleev

Periodic table Vertical columns – groups –Group 8 – noble gases, do not react Horizontal rows – periods

Isotopes Isotope – atoms of same element that differ in # of neutrons Carbon 14 is a radioactive isotope Used for medical procedures – tracers Radiation can be used to sterilize and beneficial

Bohr Model – Niels Bohr orbital (volume of space) Energy levels –electron shells of 2, 8, 8 –Ex. Sulfur – 16 3 rd period (3 shells), 6 th group, 6 electrons in outer shell Octet rule – stable if outer shell is full

Elements and compounds Compound – atoms of 2 or more different elements bond together Molecule – smallest part of a compound that still has the properties of that compound

Bonding Ions – electrically charged particles Ionic bond – gives or receives an electron –NaCl Covalent bonds – 2 atoms share electrons –Double covalent bond – 2 atoms share 2 electrons ex. Oxygen gas

bonding Nonpolar covalent bond - sharing of electrons between 2 atoms is fairly equal Polar covalent bond – unequal sharing of electrons ex. Water Hydrogen bonding – caused by polarity of hydrogen and oxygen in water molecule, DNA

Chemistry of water All living things 70 – 90% water Water molecules cling together with hydrogen bonding Properties: –High heat capacity –High heat of vaporization –A solvent –Cohesive and adhesive –High surface tension –Frozen water is less dense than liquid water

High heat capacity slow to heat or cool –Calorie – amt of energy to convert 1 g of water 1 C Why important??

High heat of vaporization liquid to gas –Hydrogen bonds must be broken –Allows for efficient way to release excess body heat

Water is solvent Solution – contains dissolved substances Solute – the substance dissolved Dissociation of water –Na+ attracted to oxygen -, Cl- attracted to hydrogen+ Hydrophillic – attracted to water Hydrophobic repel water (nonpolar)

Cohesive and adhesive Cohesion – attracted to each other Adhesion – attracted to other surfaces –Capillary action High Surface tension – strong force between water molecules –Water striders

Frozen water is less dense than liquid water Water cools, molecules move together –Hydrogen bonding is more rigid and more open –Less dense – floats What would happen if ice did not float?

Acids and bases Hydrogen ions (H+) Hydroxide ions (OH-) Acids – High H+ concentration when dissociation in water –Lemon juice, vinegar, tomatoes Basic – low H+ concentration, release hydroxide ions –Ammonia, rel

pH scale Indicates acidity and alkalinity of a solution 0 – 14, 7 is neutral H+ = OH- Below 7 = acid Above 7 = basic –Each unit has 10 times the H+ of the previous unit as you move down

Buffers Chemical s that keeps pH within normal limits Resist pH changes because they can take up excess H+ or OH- Blood = 7.4 –If drops = acidosis, rises = alkalosis –Carbonic acid/ bicabonate ions in body to regulate pH