“CHEMISTRY OF LIFE” ATOMIC STRUCTURE

ELEMENTS: A SUBSTANCE THAT CAN NOT BE BROKEN DOWN INTO A SIMPLIER SUBSTANCE. ELEMENTS CONSIST OF ONE TYPE OF ATOM. These four elements make up 96% of living things c H O N CARBON HYDROGEN OXYGEN NITROGEN

ATOMS: aTOm: Greek for “unable to be cut” Atoms are the building blocks of an element. Atoms consist of three sub-atomic particles: – Protons: Positively charged particles ( p+) – NEUTRONS: Particles with no charge (n°) – Electrons: negatively charged particles (e-)

ATOMIC SYMBOLS: Reading the atomic symbol Atomic Number = The Number of Protons and Also the Number of Electrons Atomic Mass = The Number of Protons Added to the Number of Neutrons The small # is always the Atomic Number & the larger # is always the Mass Number !

Energy levels: Protons (p+) and neutrons (n°) Are located in the nucleus Electrons are located in Energy Orbitals outside of the nucleus *Ist Energy Orbital= 2e- *2 nd Energy Orbital= 8e- *3 rd Energy Orbital= 8e- *There is a “jumping” of e- between the 3 rd & 4 th Energy Level: We will fill using

OK….Let’s Practice! 96% of Your Body Is Made Up Of Four Elements on the Periodic Table: – C Carbon – H Hydrogen – O Oxygen – N Nitrogen Construct the Atomic Structure Diagram for Each of these elements! We will Do the First one Together

ISOTOPES Isotopes: atoms of the same element that have different # neutrons – EX: C-14 Isotopes are identified by their Mass Number (# protons + # neutrons) All isotopes of the same element have the same chemical properties

Radioactive Isotopes Radioactive Isotopes: isotopes with unstable nuclei and break down at a constant rate over time Although possibly harmful, radioactive isotopes can be used to: – Determine age of rocks and fossils – Treat cancer – Kill food-spoiling bacteria

COMPOUNDS Substance composed of 2 elements chemically combined. Compounds form molecules. Examples: NaCl (salt); C 6 H 12 O 6 (sugar)

COVALENT BOND Formed when 2 atoms share 1 or more pairs of electrons. Prefix Co- means with/together. Example: Hydrogen gas

Types of Covalent Bonds: Single: 2 electrons shared Double: 4 electrons shared Triple (rare): 6 electrons shared

IONIC BONDS Ion: an atom that has a positive or negative charge Formed when Electrons are completely transferred from one atom to another.

IONIC BONDS (con’t) Positive Ion: an atom that has lost a valence electron(s) – Also called cation Negative Ion: an atom that has gained a valence electron(s) – Also called anion

For example, during the reaction of sodium with chlorine: -Sodium (on the left) loses its one valence electron to chlorine (on the right), -a positively charged sodium ion (left) and a negatively charged chlorine ion (right). resulting in

Solutions Solution: mixture in which all components are distributed evenly – Solute: substance being dissolved (ex: sugar) – Solvent: substance doing the dissolving (ex H 2 O) – Concentration: amount solute per solvent Saturated soln.: can not dissolve any more solute

Mixture A combination of substances in which the individual components keep their own properties Example: – Sand & Sugar When you stir the sand & sugar together, you can still tell the sand from the sugar.

Dissociation of Water Water molecules can react to form ions H 2 O → H + + OH - Or: Water → Hydrogen ions + Hydroxide (Hydronium)ions. Because the # of positive ions = # negative ions, water remains neutral

The pH Scale Used to indicate the concentration of hydrogen ions (H + ) in a solution Scale ranges from 0-14 At pH of 7, the number of H + ions is equal to the number of OH - ions Pure water has a pH of 7 (“neutral”)

pH (con’t) When pH of a solution is less than 7: – there are more H + ions than OH - ions – These solutions are called Acidic When pH of a solution is greater than 7: – there are less H + ions than OH - ions – These solutions are called Basic

Acids An acid is any compound that forms H + ions when mixed in a solution Turn Blue litmus paper → red Acids have pH levels below 7

Bases Base: a compound that forms OH - ions when mixed in a solution – Also called “Alkaline” solutions Turns red litmus paper → blue Bases have pH levels greater than 7

Buffers Buffers: compounds that help prevent sharp changes in pH within cells Help protect living tissue by keeping pH within cells between 6.5 and 7.5