Chem 212 chapter 2
Chem 212 chapter 2 Chem 212
University of Louisiana at Lafayette
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This 10 page Class Notes was uploaded by Kaylee Friou on Monday September 19, 2016. The Class Notes belongs to Chem 212 at University of Louisiana at Lafayette taught by Jennifer De Guzman in Fall 2016. Since its upload, it has received 5 views. For similar materials see Survey of Chemistry for Education Majors in Chemistry at University of Louisiana at Lafayette.
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Date Created: 09/19/16
Chapter 3: Elements and the Periodic Table 3.1 The Building Blocks of Matter A. The Atom –Dalton’s atomic theory (1802) • An _atom_is the smallest particle of matter_. • An _atom is the smallest unit of an element . • Atoms of one element are _(mostly) identical__. • Atoms one element are _different_ from atoms of _another element_. B. Elemental Symbols • A symbol represents each element. • Some are easy: C H Carbon Hydrogen • Some are harder to see: Au Sn Gold Tin • Know name = symbol for #1 - 20 for Test 1__; Know the entire list from Moodle for __Test 2__. C. Compounds are made up of __2 or more elements_ joined by chemical bonds__. H2O C2H6O • The smallest unit of a compound is a _molecule_. • _Subscripts_ are whole numbers that show _how many_ __atoms___ of each element are present in each molecule of the compound. Bad: HO1/2 C0.33HO0.18 • All molecules of a compound are _identical_. D. Smallest Form 1. Most elements are _monoatomic__: the smallest form is a singular atom. 2. __Diatomic Elements__: elements whose smallest unit is a __2 atom molecule_ Diatomic Elements: H, N, O, F, Cl, Br, I H – H 1 molecule of H2 3.2 Inside the Atom Nucleus – tiny volume of space at the center of each atom A. The Subatomic Particles Particle Mass Charge Location (amu) Protons (p) 1 +1 Nucleus Electrons (e ) 0 -1 Surrounding Neutrons (n) 1 0 Nucleus B. The Atomic Number 1) On the Periodic Table: 3 <-atomic # -number of protons Li 6.94 <- atomic mass • Each element is defined by its number of protons__. 2) For a neutral atom: • number of protons = number of electrons • The charges of each atom will cancel Li C _3_p and _3_e - 6_p and _6_e - +3_ + _-3_ = +6_ + -6_ = 0 _0 3.3 Ions Ions are formed when an atom __gains or loses electrons___. A. Positive Ions - forms when an atom loses e- — +1 H — 1e = H 1_ p 1 p _1_ e- 0 e- B. Negative Ions- forms when an atom gains e+ — —3 N + 3e = N _7 p _7_ p - - _7_ e _10 e How many electrons are gained or lost to form the following ions? O—2 V+3 K+1 2 gained 3 lost 1 lost 10 e- total 20 e- total 18 total 3.4 Isotopes • Isotopes – atoms which have the __same #s_ of _protons (p)_ and _electrons (e-)_, but __different #_ of _neutrons_. • This affects the mass_ of the atom • Isotope Notation: mass number=protons+neutrons Element Atomic #- protons A E Z • Most elements exist in nature as several different isotopes. 1 2 3 1H 1H 1H p =1 p =1 p = 1 — — — e =1 e = 1 e = 1 n =1-1=0 n = 2-1=1 n = 3-1=2 Bringing all the concepts together: 110 78 46Pd+4 3As –3 p =46 p =33 e =46-4=42 e = 33+3=36 n = 110-46=64 n = 78-33=45 3.5 Atomic Mass • The Atomic Mass is the _weighted average_ of the masses of _all known isotopes_ of an element. • The more _abundant_ isotopes have __more of an impact__ on the Atomic Mass; rare_ isotopes have less of an effect. Three isotopes of H: abundant: rare: 1 2 3 1H 1H 1H Atomic Mass of H: • The Atomic Mass is therefore closest to the mass number__ of the _most abundant__isotope. • Which is the most abundant isotope of Br? 81 79 80 35r 35Br 35Br • Write the isotope notation for the most abundant isotope of each, based upon its Atomic Mass: 12 40 C Ar 6 18 3.7 The Periodic Table of the Elements A. Organization 1. Groups – the vertical columns 2. Periods – the horizontal rows 3. Metals – left side of table • luster- shiny • good conductors of heat and electricity • malleable and ductile • solid at room temperature • Aluminum is a metal 4. Non-metals – right side of table • dull • good insulators • brittle (not malleable or ductile) • can be solid, liquid, or gas at room temperature • Hydrogen is a non-metal 5. Metalloids – on the zigzag line • have properties of both • useful as semiconductors • B, Si, Ge, As B. Group Names 1A – groups that contain representative elements (Alkali metals) “middle” – transition metals 2A – Alkaline Earth metals 8A- Noble Gases (doesn’t want to combine) 7A- Halogens C. Trends of PeriodiTble 1. Atomic Size (Atomic Radius) Which would have the largest atomic size? NO 2. PS Atomic size increases Atomic size increases Ionization Energy – energy needed to remove a single electron from an atom Which would have the largest ionization energy? Ti V Zr Nb 3. Electronegativity – attraction of the outermost electrons to the neucleus Which would have the smallest electronegativity? B C Al Si
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