Elements and Symbols 1 letter symbols C Carbon N Nitrogen O Oxygen 1 Capital letter Element Pure substance that can not be broken down into simpler substances by a chemical reaction 2 letter symbols ID: 769922
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Elements and Symbols 1 letter symbolsC = CarbonN = NitrogenO = Oxygen1 Capital letter Element – Pure substance that can not be broken down into simpler substances by a chemical reaction 2 letter symbols Cl = Chlorine Ba = Barium Au = Gold 1 Capital and 1 lower case letter
CompoundPure substance formed by chemically combining two or more elementsH element + O element can make H2O compoundCO2, HCl, C3H8 Atom smallest unit of an elementMolecule smallest unit of a compound
Atom: basic unit of matter Smallest unit of matter that individually retains the chemical characteristics of an elementConsists of a dense positively charged central region, called a nucleus, surrounded by a negatively charged cloudContains three types of subatomic particles: Proton Neutron Electron
The Proton Charge = + 1.602×10−19 CCalled “+1” for clarity Located in nucleus of atom Mass = 1.672 x 10 –24 g Approx. 1 unified atomic mass unit (u) 1 amu = 1.66 x 10–24 g
The Neutron No charge (0 C)Located in nucleusMass = 1.675 x 10–24 gApprox. = 1 amu
The Electron Charge = –1.602 x 10–19 CCalled “–1”Located outside nucleus in an e- “cloud ” Mass = 9.109 x 10 -28 g Approx. = 0 amu
RecapWhat are the three subatomic particles?Where are they located in the atom?What are their weights in atomic mass unitsWhat are their charges?
Dmitri Mendeleev (1834-1907) Russian chemistArranged elements in horizontal rows in order of increasing atomic weightStarted new rows in order to make columns of chemicals with similar characteristicsLeft spaces open for elements yet to be discovered
Classification of the Periodic Table Classification by Physical Properties
Metals ShinyConduct electricityDuctileCan be drawn through wiresMalleable (Shapeable)High M.P. & B.P Solids @ room temp Except Hg
Non-Metals Don’t tend to conduct wellNot usually ductileTend to be brittleLow M.P. & B.P.Many are gases at r.t.
Metalloids Have chemical characteristics in between those of metals and non-metalsIncludes elements: B (Boron), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), Astatine (At)
Classification by Chemical Properties
Alkali Metals Group 1 (1A)Li, Na, K etc.Soft, shiny metalsConduct heat and electricityReact violently with H2 O Form H 2 (g) and ( basic) solutions
Akali(ne) Earth Metals Group 2 (2A)Be, Mg, Ca etc.Not as reactive as Alkali Metals, but still quite reactiveTend to make basic solutions when placed in water
Transition Metals Groups 3B-8BTend to have high densities and B.P.All are metalsOften used for electrical conduction Often have vivid colors when in solution Used for pigments
Colors of Transition Metal Compounds IronCobaltNickel Copper Zinc
Lanthanides Elements 57-71Lanthanum (La) to Lutetium (Lu)Commonly used in lasersCan deflect UV and infrared rays
Actinides/Actinoids Elements 89-103Actinium (Ac) to Lawrencium (Lr)Only Actinium, Thorium (Th), and Uranium (U) occur naturally Others created by neutron bombardment Radioactive
Groups 3A – 6A No common nameBoundary between metals and non-metals occurs hereContains the metalloidsContain elements abundant in earth’s crust, atmosphere, and living things C, N, O, Si
Halogens Group 7AF, Cl, Br, I, AtVery reactive with many compoundsLike to form di atomic molecules F 2 , Cl 2 , Br 2,
Noble Gases Group 8AHe, Ne, Ar, Kr, Xe, RnVery unreactive Don’ t like to bond to other molecules Generally not abundant
ProblemsWrite down an element from each of the groups1. Noble Gas (example-- He aka Helium)2. Lathanide3. Alkali metals4.Halogens5. Actinides6. Alkaline metals 7. Element that is abundant in living organisms
Atomic number -- Also number of protons-- Usually the number of electrons as wellAtomic symbol -- 1 or 2 letter symbol Average atomic weight or Approximate Mass number -- Also number of protons + number of neutrons
Can also represent by omitting atomic number (Z) since it is implied by the element Which atom does the picture below represent?
Identify number of protons, the mass number, and number of neutrons for the following elements.
Isotopes Atoms of the same element that have different atomic massesSame number of protonsDifferent # of neutrons Percent Abundance - amount of each isotope that occurs naturally
Average atomic massWeighted average of the mass of naturally occurring isotopes of a particular element reported in atomic mass unitsZi = mass number of smallest isotope% abd = percent abundance[Zi(% abd) + Zi+1(% abd) + Zi+2(% abd) + ……]Example-- [20(0.9092) + 21(0.0026) +22(0.0882)] = 20.179 amu ~ 20.18 amu
Problems Lithium has two natural isotopes, 6Li and 7Li, which have percent abundances of 7.5% and 92.5% respectively. What is the average atomic mass of Lithium?
Using the percent abundances below, calculate the average atomic mass for Carbon C-12 = 98.890%C-13 = 1.110%C-14 = 0.0000000001% Antimony ( Sb ) has two stable isotopes, 121 Sb and 123 Sb with masses of 120.9038 u and 122.9042 u, respectively. Calculate the percent abundances of these two isotopes
Atomic Orbitals and Electron Configurations
382.5 Electronic Structure An electron is confined to a specific region around the nucleus, giving it a particular energy.The regions occupied by electrons are called principal energy levels or shells (n ). The shells are numbered n = 1, 2, 3, etc. Electrons in lower numbered shells are closer to the nucleus and are lower in energy. Electrons in higher numbered shells are further from the nucleus and are higher in energy.
392.5 Electronic Structure Shells are divided into subshells, identified by the letters s, p, d, and f. The subshells consist of orbitals . An orbital is a region of space where the probability of finding an electron is high. Each orbital can hold two electrons.Subshell Number of Orbitals s p d f 1 3 5 7 increasing energy
S orbitals Spherical shapeLowest energy of the orbitals
P Orbitals Higher energy than s orbitalsDumb bell shapedCome in 3’spx, p y, p z
D Orbitals Higher energy than s and p orbitalsDouble dumb bell shape or single dumb bell with a donutCome in 5’sd xy, dxz , d yz , d x2-y2 , d z2
F Orbitals Higher energy than s, p, and dCome in 7’s
How do we know where our electrons are?Electrons will seek the lowest E orbital available first
Hydrogen Helium 1 Lithium? Pauli Exclusion Principle : orbitals may hold up to two electrons. The electrons must be of opposite spin
Hund’s Rule : electrons pair only after each orbital of equal energy is occupied by a single electron
Problems Determine the electron configurations for the following atomsNONeNa MgAl S Fe W
Noble Gas Abbreviation The electron configuration of the noble gas that precedes the element in question is represented by the noble gas’ bracketed symbolExample: C = 1s22s22p2 = [He] 2s22p 2 Write the electron configurations for Vanadium and Bismuth
Valence ElectronsElectrons in the outermost(valence) shellThe shell with the highest number C = 1s22s22p2 --- 2 is highest number count up electrons in all the valence orbitals2 electrons in the 2s orbital and 2 electrons in the 2p orbital 2 + 2 = 4 valence electronsP = 1s22s22p63s23p3 ------- 3 is highest number2 + 3 = 5 valence electronsUsing the Noble gas abbreviation can help
Electron dot symbolsValence electrons represented with dots Dots are placed on four sides of the element symbolUp to 2 dots max per side, must fill up all sides before pairing up dots
ProblemsDetermine valence electrons for the following elements and draw the electron dot symbol for eachHLiSiBrAr Ti
Periodic TrendsAtomic number increases going to the right and going downAtomic size (how big the atom is) increases going to the left and going downIonization energy (energy required to remove a valence electron)increases going to the right and going up
Chapter 2 ReviewElement symbolsInside the atom. Proton, neutron, and electron. Charge, mass, location.Periodic Table Bonanza!! Being familiar with the table and how to use it.Metals, metalloids, non metals. Properties and which elements are from which class.Group/families of elements. Alkali metals, Alkaline metals, transition metals, Halogens, Lanthanides, etc.Atomic number and Mass number. Recognizing how many protons electrons and neutrons in an given isotope.Isotopes percent abundance. Calculating average atomic mass. Atomic orbitals. s, p, d, f orbitals, different shapes and energies.Electron configurations. Pauli exclusion principle, Hunds rule, noble gas, abbreviation.Valence electrons and Electron dot structurePeriodic trends