Chem 105a Week 2 Notes
Chem 105a Week 2 Notes CHEM 105A
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This 5 page Class Notes was uploaded by Emma Morrissey on Friday September 9, 2016. The Class Notes belongs to CHEM 105A at University of Southern California taught by Thomas Michael Bertolini in Fall 2016. Since its upload, it has received 14 views. For similar materials see General Chemistry in Chemistry at University of Southern California.
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Date Created: 09/09/16
Chapter 2 - Atoms and Elements ● Scanning Tunneling Microscopy ○ STM makes it possible to view atoms ○ There is exactly one atom at the end of the probe’s tip to create an image with an atomic resolution ○ Runs a current from the tip to the surface of the object; sensitive to distance ● The Periodic Table ○ Periods (rows) ○ Groups/Families (columns) ○ Metals ■ Solids at room temperature except Hg ■ Shiny ■ Conduct heat and electricity ■ Malleable (moldable, made into sheets) ■ Ductile (can be pulled into wire) ■ Form cations in reactions (positively charged ions; lose electrons) ■ Account for about 75% of elements ■ Found to the left on the periodic table ■ Colorless except Cu (Red) and Au (Yellow) ■ Gold ● The most malleable metal ○ Nonmetals ■ Exist in all three states ■ Poor conductors (insulators) ■ Brittle (will shatter) ■ Form anions in reactions (negatively charged ions) ■ Found on the right ○ Metalloids ■ Shiny ■ Brittle ■ Semiconductors ● Can gain or lose electrons ○ States at room temperature (25 C) ■ Gases: ■ Liquids: Br, Hg ■ Solids: all others ○ Classification ■ Representative or Main Group elements ● Groups 1,2,13-17 ■ Transition metals ■ Alkali metals (basic elements; react very exothermically to form Hydroxide atoms) ■ Alkaline Earth metals (won’t react with water, but with aqueous acids) ■ Halogens ■ Noble Gases ○ Oxidation states ■ Cu +1, 2 ■ Ag 1 ■ Au 1,3 ■ Main groups are predictable ● Subatomic Particles ○ Protons and neutrons comparable in mass ○ Mass of electron is much smaller ○ Charges: 1.60218 E-19 Coulombs ○ Atomic nucleus- ball bearing, entire atom- football stadium ■ Empty space ● Atomic Symbols ○ Atomic number (Z) ■ Equal to the number of protons in the nucleus ■ Defines the element ○ Mass Number (A) ■ Neutrons plus protons ■ Isotopes have different number of neutrons ○ Atomic Symbol (X) ● Isotopes ○ All isotopes of an element have ■ The same chemical reactivity ■ The same number of protons ■ Different numbers of neutrons and therefore different masses ○ Over 90% of known isotopes are radioisotopes, and every element has at least one radioisotope ○ Identify an isotope based on the number of neutrons ■ The most common isotope of Hydrogen has no neutrons ■ Radioisotopes cause cancer ● Isotopes and ions ○ Ions have a net charge; they have different numbers of electrons and protons ● Atomic Mass ○ Mass is relative; to measure an objects’s mass is to compare it to a metal cylinder in France ○ C-12 is defined as having exactly 12 atomic mass units (amu) is the reference for atomic masses ■ Therefore, 1 amu = (mass C-12)/12 ○ Atomic masses on the periodic table are averages ■ No actual U atom has a mass of 238.03 amu ■ Average atomic mass is calculated from the mass and abundance of each isotope ○ Calculating average atomic mass of an element ■ Relative abundance (percent) ■ Atomic mass of each isotope ■ Find the weighted average of the atomic masses ■ (mass 1)(percentage of mass 1)+(mass2)(percentage of mass 2) +(mass z)(percentage of mass z) ■ Mass number is an inexact number; it is a calculated value ● Mass spectrometer ○ Used to calculate the mass of ○ ● The Mole ○ A mol is the number of atoms in exactly 12 g of pure C-12 23 ○ 1 mol = 6.02214 x 10 particles ■ Known as Avogadro’s number N ■ Inexact number; measured value ○ The mole allows for conversions between mass and number of particles ○ One mole of seconds = 1 quadrillion years ○ 1 amu = 1 gram ● Counting atoms by moles ○ With the mass of a pure compound we can find the number of atoms in the sample and vice versa ○ Example ■ What is the mass of 12 atoms of rhodium? ○ Example ■ If 100 tons of Cu were used to make the Statue of Liberty, how many atoms does it contain? (1 kg = 2.205 lb; 2000lb= 1 English ton) CHAPTER 3 Bonds ● Compounds vs Molecular Elements ○ Atomic elements ■ Exist as single atoms ○ Molecular elements ■ The same element covalently bound to itself ● Diatomics; HOFBrINCl ● P4, S8, Se8 ○ Molecular compounds ■ 2 or more different nonmetals ○ Ionic compounds ■ Composed of cations and anions ● Naming Compounds ○ Binary ionic compounds (metal + nonmetal) ■ The metal only forms 1 cation ■ The cation (positively charged ion) is named first ● Has the same name of its parent element ■ Name the anion as (parent element root + ide) ■ Sodium Chloride ■ Barium Nitride ○ Binary Ionic Compounds (metal + nonmetal) ■ The metal forms 2 or more cations; requires a Roman numeral ○ Binary Covalent compounds (nonmetal + nonmetal) ○ Acids ● Polyatomic ions ● Cations with multiple possible charges ○ Cr Mn Fe Co Cu Hg
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