Chemistry 2 8:15:17.docx - SI Instructor Erica...

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SI Instructor: Erica Chong ( [email protected] ) SI: Monday 6:30 pm Chemistry 1145 Review Chapters 1-3 Atomic number - number of protons in an atom of any particular element = to number of electrons Mass number/atomic weight – number of protons + neutrons Isotopes: two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons giving them differing atomic masses but are the same chemically Protons = atomic # Electrons = Protons (atoms neutral) Neutrons = mass # - protons Mass # = protons + neutrons Average Atomic Mass: relative abundance: % of an elements isotopes found in nature Vertical: groups/families Horizontal : Periods Periodicy: Elements in a group often have similar properties physically and chemically
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- Lattice Energy: energy required to separate 1 mole of solid ionic compounds into its elements o Increases as distance between ions decreases o Increases as charge increases - Aufbau Principle: As protons are added 1 by 1 to the nucleus, so are electrons - Hunds Rule: lowest energy config. for an atom is one having max # of unpaired electrons allowed - Elements in the same group have the same valence electron configuration - Groups 1, 2, 13-17 are known as representative elements - Coulomb’s Law: electrical force between 2 charged objects is dependant on the size of charges and distance between them - Period Trends o Radius (atomic size): L2R Decreases: b/c of decreased shielding, valence electrons drawn closer to nucleus decreasing size of atom T2B Increases: increase in orbital size and successive principle quantum lvls o Ionization Energy & Effective Nuclear Charge: energy to remove the most loosely held electron: T2B decreases: b/c increased distance and increased shielding L2R increases: b/c as nucleus gains more protons, effective nuclear charge increases Zeff: Effective Nuclear Charge: net positive charge experienced by an electron in a multi electron atom o Electron Affinity: energy change associated w/ the addition of an electron to a gaseous atom; energy released when it is added o Associated w/ electron negativity b/c they have a negative EA o Electron Negativity & Electron Affinity: L2R increases: T2B decreases - Group Properties o Alkali Metals (1) o Alkaline Earth Metals (2) o Transition Elements (3-12) o Representative (13-16)
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o Halogens (17) o Noble Gases (18) molecular formulas- chemical formula that indicates the actual numbers of atoms in a molecule empirical formulas- chemical formulas that only give a relative number of atoms in each type of molecule Molecular mass/empirical formula mass = # that says how many times larger molecular is than empirical Determining the Empirical Formula of a Compound: C H N .1156 g of this compound reacts with O 2 to Form .1638 g of CO 2 and .1156 g H 2 O 1. use fraction of mass Carbon in CO 2 CO 2 mm = 44.01 g C mm = 12.01 12.01/44.01 2. Use this fraction and multiply it by grams of CO 2 collected : .1638 x (12.01/44.01) = .04470 g C 3. divide this mass by molar mass of original compound and multiply by 100: (.04470/.1156)x100 = 38.67% C
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