CH 18 Properties of Atoms and CH 18 Properties of Atoms and the Periodic Tablethe Periodic Table

Structure Structure of the of the AtomAtom

• Chemical symbolChemical symbol — —shorthand way to shorthand way to write element’s name; write element’s name; 1 or 2 letters1 or 2 letters

• 11stst letter letter ALWAYSALWAYS capitalized and if there capitalized and if there is a 2is a 2ndnd it is lowercase it is lowercase

• Case sensitiveCase sensitive: CO: CO≠Co≠Co

• Some use Latin Some use Latin names, names, AgAg is silver— is silver—ArgentumArgentum in Latin in Latin

• System used System used worldwideworldwide

• AtomsAtoms—basic —basic building blocks of all building blocks of all mattermatter

• Composed of:Composed of:

• ProtonsProtons—in nucleus; —in nucleus; ++

• NeutronsNeutrons—nucleus; —nucleus; neutralneutral

• ElectronsElectrons—around —around nucleus; -nucleus; -

• NucleusNucleus—positively —positively charged center of charged center of atomatom

electron

neutron

proton

QQuuaarrkkss

• QuarksQuarks—what —what protons and protons and neutrons are neutrons are made of;6 typesmade of;6 types

• Up, down, charm, Up, down, charm, strange, top & strange, top & bottombottom

• 3 arranged one 3 arranged one way=proton (pway=proton (p++) )

• 3 arranged 3 arranged another another way=neutron (nway=neutron (n°)°)

Electron modelsElectron models

• Atomic models Atomic models have changed thru-have changed thru-out historyout history

• Models showing Models showing where e- is located where e- is located also changed also changed (pg (pg 548)548)

•Bohr’s modelBohr’s model is is the one we the one we recognizerecognize

Electron Electron modelsmodels • Electron cloudElectron cloud is is

current modelcurrent model

• Cloud is the Cloud is the probable probable region region where you would where you would find an e-find an e-

• Cloud 100,000 Cloud 100,000 times larger than times larger than nucleus! But e- is nucleus! But e- is MUCHMUCH smaller smaller than a pthan a p++

Masses of AtomsMasses of AtomsSec 2Sec 2

• Neutral atomNeutral atom— — equal # of p+ and e-equal # of p+ and e-

• Atomic mass unitAtomic mass unit (amu) used to (amu) used to measure atomic measure atomic particlesparticles

• Equal to 1/12th the Equal to 1/12th the mass of a carbon mass of a carbon atomatom

Masses of AtomsMasses of Atoms Sec 2 Sec 2 cont.cont.

•Atomic #Atomic # = # of p = # of p++

•Atomic mass=Atomic mass=# of # of pp++ and n° and n° (# above (# above chem. symbol on your chartchem. symbol on your chart—larger #)—larger #)

• Atomic mass – atomic # = # of Atomic mass – atomic # = # of n°n°

• IsotopesIsotopes—atoms of —atoms of the same element the same element that have a that have a different # of n°different # of n°

Sec 3 Periodic Table Sec 3 Periodic Table

• Dmitri MendleleevDmitri Mendleleev——Russian chemist (late Russian chemist (late 1800’s) arranged 1800’s) arranged elements in order of elements in order of increasing atomic massincreasing atomic mass

• Left blank spaces due to Left blank spaces due to undiscovered elementsundiscovered elements

• Vertical columns (18) Vertical columns (18) called called groups/familiesgroups/families

• # of outer e- are the # of outer e- are the same in each groupsame in each group

• Chemical properties are Chemical properties are the same for the the same for the elements in each groupelements in each group

• Horizontal rows called Horizontal rows called periodsperiods

• MetalsMetals—all elements left of the —all elements left of the stair stepstair step• Properties: solids at room temp (except ?),Properties: solids at room temp (except ?),

shiny, good conductors of heat and electricityshiny, good conductors of heat and electricity• MetalloidsMetalloids—elements near the —elements near the stair stepstair step• Have properties of both metals and non-metals Have properties of both metals and non-metals • Non-metalsNon-metals—right of —right of stair stepstair step• Properties: most are gases, some brittle solids, poor Properties: most are gases, some brittle solids, poor

conductors of heat/electricity conductors of heat/electricity • Groups 3Groups 312 called 12 called TransitionTransition elements: metals, but elements: metals, but

have properties not found in elements of other groupshave properties not found in elements of other groups

• Energy levels of Energy levels of e-e-

• 11stst level level, closest , closest to the nucleus, to the nucleus, lowest E, only lowest E, only holds holds 2 e-2 e-

• 22ndnd level level holds holds 8 8 e-e-

• 33rdrd level level holds holds 18 18 e-e-

• 44thth level level holds 32 holds 32

e-e-

• e- dote- dot diagramsdiagrams—represents the outermost e- of —represents the outermost e- of an elementan element

• Called Called Lewis structuresLewis structures

• Chemical symbol and the # of e- in the outer Chemical symbol and the # of e- in the outer level placed around the chem symbol using dots level placed around the chem symbol using dots