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Chapter 3 – Chemical Foundations. Chemical Foundations – students will identify elements, ions and molecules; be able to write formulas and names for a variety of compounds. Greeks first to explain chemical changes. All Matter made of 4 “Elements”: Fire, Earth, Water, & Air.
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Chapter 3 – Chemical Foundations Chemical Foundations – students will identify elements, ions and molecules; be able to write formulas and names for a variety of compounds.
Greeks first to explain chemical changes. All Matter made of 4 “Elements”: Fire, Earth, Water, & Air
Robert Boyle: 1st Scientist to recognize importance of careful measurements and experimentsOxygen Most abundant element on Earth 115 current number of elements*88 # of naturally occurring elements
Trace Elements Human body needs tiny amounts of these elements Iron [Fe] – Hemoglobin and blood
ElementSymbol shorthand method of representing elements 1st letter always a CAPITAL 2nd letter always a lower case e.g. Cl or He or Fe
JohnDalton – proposed Atomic Theory proposed atom model as a tiny, SOLID sphere All elements made up of atoms. All atoms of an element are identical. Atoms of 1 element differ from every other element. Different atoms can combine to form compounds Atoms are indivisible. What does that mean?
Compound substance composed of the atoms of two or more elements and ALWAYS contain exactly the same number of those atoms
ChemicalFormula atoms areindicated by the element symbols and the number of each type of atom is indicated by a subscript e.g. H2O or NH4OH or C6H12O6 complete the Self-Check on pg. 55 in the World of Chemistry textbook
J.J. Thomson late 1890’s discovered the electron proved that e- was NEGATIVE theorized that there must be apositive area in atom because he knew that atoms were NEUTRAL
William Thomson (Lord Kelvin) building on J.J. Thomson’s work, proposed the Plum Pudding atom model “Plum Pudding” modele- positive matrix
Ernest Rutherford – “Gold Foil” Exp. shot alpha particles at a VERY thin piece of gold foil amazed when MOST of the alpha particles passed right through the foil a few alpha particles were deflected small # were bounced straight back How did Rutherford interpret these seemingly “WRONG” results?
Rutherford: Mass of atom located in Middle Mass in middle is Positively Charged Dense center named Nucleus Nucleus must contain Protons Protons had same size charge as electron but positive Electrons must be located somewhere outside of nucleus
Part 2Isotopes: Atoms of SAME Element a. same number of protons b. same number of electronsc. DIFFERENT # of Neutrons Chadwick proved existence ofNeutrons in nucleus of atoms
Atomic Number (Z) - # of protons in the nucleus of an atom Mass Number (A) – SUM of theProtons and Neutrons in the nucleus of an atom
A ---------- Atomic NumberX---ElementZ ---------- Mass #
6CCarbon – 6 protons, and 14 6 electronsHow many Neutrons? Z – A = Neutrons 14 – 6 = 8 neutrons
Periodic Table First Periodic Table – 1869 -- DemitriMendeleevarranged by AtomicWeightsNow arranged by Atomic Number
What is the Difference between Atomic Weights and Atomic Number? Atomic Weight is the average weight of Many atoms of an element. Atomic Number is the Number ofProtons in the Nucleus of an Atom. [and the number of electrons] In 1869, the proton had not yet been discovered!
Remember: Alkali Metals [group 1], Alkaline Earth Metals [group 2], Halogens [group 7]Noble Gases [group 8]Groups are also called families.
What is the name of all of the Metals in the middle of the Periodic Table?TransitionMetals – Almost all are solids at room temperature.
Where are Metals, Nonmetals, & Metalloids located on the Periodic Table? Most elements are the metals. Located on the left side of Periodic TableMetals – groups 1-13Nonmetals – groups 14-16Metalloids – along the stair step line from Boron to Tellurium
Physical Properties of Metals: Metals are good conductors of both heat and electricity Malleability – can hammer into thin sheetsDuctility – can be formed as wiresLustrous – shiny appearance
Nonmetals – Located on the right side of the Periodic Table small number of elements lack most of the properties of metals many are gases at room temperature
Each group has a charge that represents the number of electrons in it’s outer energy level. Example: group 1 – has 1 electron in their outer level, so they will have a +1 charge; group 2 - +2; group 3 - +3; group 4 - +/- 4 [usually -4]; group 5 - -3; group 6 - -2; group 7 - -1 and group 8 – 0 since they are chemically stable and their outer energy level is full. Group 8 Group 6 Group 1 Group 2 Group 3 Group 4 Group 5 Group 7