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Download Unit 4 Study Guide Groups to know: Alkali Metals
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Unit 4 Study Guide Metals Nonmetals Noble Gases Noble Gases -nonreactive -no electronegativity Halogens Halogens -most reactive nonmetals Alkali Metals Alkali Metals -most reactive metals Alkaline Earth Metals Groups to know: Transition Metals Metals -malleable, ductile, high density, lustrous (shiny), conduct heat and electricity well Nonmetals -Hydrogen is a nonmetal even though it is on the metals side -brittle if solid, lower densities, dull, insulators Some Definitions: Period -horizontal rows; equal the energy level of the valence electrons Group -vertical columns on the periodic charge; elements in the same groups tend to have similar properties Ion -charged atom Cation -positively charged atom; lost electrons; smaller than the neutral atom Anion -negatively charged atom; gained electrons; larger than the neutral atom Isotope -atoms of the same element, but different numbers of neutrons Ionization Energy -amount of energy needed to remove a valence electron; forms a cation Electronegativity -attraction of an atom in a compound for a nearby electron; forms an anion Trends: Atomic Radius Metal Reactivity Ionization Energy Atomic Radius Metal Reactivity Atomic Radius: Anion > Neutral atom > Cation Fr (francium) is the most reactive metal and has the largest atomic radius He (helium) has the highest ionization energy F (fluorine) has the highest electronegativity and is the most reactive of all nonmetals *Check your notes to know WHY these trends occur! You must know this!!!* F Ionization Energy Electronegativity Nonmetal Reactivity Electronegativity Nonmetal Reactivity Fr He Atomic Theory: John Dalton 1803 – First Modern Atomic Theory -5 Postulates on the atom: 1. Elements are composed of atoms, which are very small, indivisible, indestructible particles. (false) 2. All atoms of the same element are exactly identical. (false – isotopes!) 3. Atoms of different elements have different properties. (true) 4. Atoms combine in small, whole-number ratios to form compounds. (true) 5. Atoms of one element cannot change into an atom of a different element during a chemical reaction. (true) J. J. Thomson - discovered the electron using cathode ray tubes -proposed “Plum Pudding Model” – electrons move randomly in a positively charged, amorphous cloud Ernest Rutherford - discovered the nucleus in the Gold Foil Experiment -proposed that the positive charge is located in the nucleus and that electrons somehow orbit the nucleus Gold Foil Experiment: Hypothesis: If the Plum Pudding Model is true, all alpha particles should go through a piece of gold foil Result: Some alpha particles bounced back Modified Theory: The atom has a very dense, positively charged core (the nucleus) Niels Bohr - Bohr Model -proposed that electrons orbit the nucleus in distinct energy levels like planets around the sun Modern Atomic Theory -Electrons move randomly around the nucleus in the electron cloud -We cannot know the exact speed and location of an electron at the same time; we can calculate the general area where an electron can be found based on the amount of energy it has Atomic Number = # of protons = identity of atom Symbol: FIRST LETTER CAPITALIZED; second letter lower case Average atomic mass = the average mass of all the different isotopes Know how to do these calculations!!! Example of Bohr Model (not an accurate picture of the atom…) Particle Electron Location Charge electron cloud -1 Size very small Changes… charge (ion) Neutron nucleus 0 same as proton mass # (isotope) Proton nucleus +1 same as neutron identity of atom Know how to calculate these! Oxygen – 16 oxygen atom with mass number 16 p+n mass number = → 16 atomic → 8 number = p O 2- ionic charge = p - e ←
