Electron Dot NotationElectron Dot Notation

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VocabularyVocabulary

Valence electrons ?Valence electrons ?Electron- dot notations ?Electron- dot notations ?Octet rule ?Octet rule ?

Page 169 & 170Page 169 & 170

Valence ElectronsValence Electrons

The electrons responsible for the The electrons responsible for the chemical properties of atoms are chemical properties of atoms are those in the those in the outerouter energy level. energy level.

Valence electronsValence electrons - The - The ss and and pp electrons in the electrons in the outerouter energy level energy level– the highest occupied energy levelthe highest occupied energy level

Keeping Track of ElectronsKeeping Track of ElectronsAtoms in the Atoms in the samesame column... column...–Have the Have the samesame outer electron outer electron

configuration.configuration.–Have the Have the samesame number of number of

valence electrons.valence electrons.Easily found: the Easily found: the group number group number representative elements tell the representative elements tell the number of valence electrons.number of valence electrons.

Example: Example: Group 2A: Be, Mg, Ca, etc.Group 2A: Be, Mg, Ca, etc.have 2 valence electronshave 2 valence electrons

Electron Dot notations Electron Dot notations oror diagramsdiagrams

A way of keeping track of A way of keeping track of valence electrons.valence electrons.How to write them?How to write them?Write the Write the symbolsymbol first. first.Then put dots to represent Then put dots to represent the valence the valence electronselectrons..According to Hund’s rule, According to Hund’s rule, electronselectrons don’t pair up until don’t pair up until they have to they have to

X

The Electron Dot diagram for Nitrogen

Nitrogen has 5 valence electrons.

First we write the symbol.

NThen add 1 electron at a time to each side.Until they are forced to pair up.

Electron Configurations for Electron Configurations for CationsCations

Metals Metals loselose electrons to attain noble electrons to attain noble gas configuration.gas configuration.

Metals form Metals form positivepositive ions ( ions (cationscations))

If we look at the electron configuration, If we look at the electron configuration, it makes sense to lose electrons:it makes sense to lose electrons:

Na Na 1s1s222s2s222p2p663s3s11 1 valence electron 1 valence electron

NaNa1+1+ 1s1s222s2s222p2p66 noble gas configuration noble gas configuration

Electron Dots For CationsElectron Dots For Cations

Metals will have few valence Metals will have few valence electrons (usually 3 or less)electrons (usually 3 or less)

Ca

Electron Dots For CationsElectron Dots For Cations

Metals will have few valence electronsMetals will have few valence electrons

These be given awayThese be given away

Ca

Electron Dots For CationsElectron Dots For Cations

Metals will haveMetals will have few few valence electronsvalence electrons

These will be given awayThese will be given away

Forming positive ionsForming positive ions

Ca2+Now make Li an ion.

Pseudo-noble gas configuration

Electron Configurations for Electron Configurations for AnionsAnions

Nonmetals Nonmetals gaingain electrons to attain electrons to attain noble gas configuration.noble gas configuration.

Nonmetals form Nonmetals form negativenegative ions ( ions (anionsanions))

Example:Example:

S S 1s1s222s2s222p2p663s3s223p3p44 6 valence electrons 6 valence electrons

SS2-2- 1s1s222s2s222p2p663s3s223p3p66 noble gas noble gas configuration.configuration.

Electron Dots For AnionsElectron Dots For Anions

Nonmetals will have many valence Nonmetals will have many valence electrons (usually 5 or more)electrons (usually 5 or more)

They will They will gaingain electrons to fill outer shell. electrons to fill outer shell.

P P3-

Stable Electron ConfigurationsStable Electron Configurations

All atoms react to achieve All atoms react to achieve noblenoble gasgas configuration.configuration.

Noble gases have 2 Noble gases have 2 ss and 6 and 6 pp electrons electrons for a total of for a total of 88 valence electrons to meet valence electrons to meet the the octet ruleoctet rule..

Ar

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Teacher Notes:Chemical Bonding 6 min(nisd002 research)1. Introduction to chemical bonding 1:152. Atoms and Bonding 1:403. Electrons and Energy Levels 1:014. Stability & Chemical Bonds 1:37