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Chapter 7Chapter 7

Atomic StructureAtomic Structure

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The Periodic Table The Periodic Table Developed independently by German Developed independently by German

Julius Lothar Meyer and Russian Julius Lothar Meyer and Russian Dmitri Mendeleev (1870”s)Dmitri Mendeleev (1870”s)

Didn’t know much about atom.Didn’t know much about atom. Put in columns by similar properties.Put in columns by similar properties. Predicted properties of missing Predicted properties of missing

elements.elements.

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Aufbau PrincipleAufbau Principle Aufbau is German for building upAufbau is German for building up As the protons are added one by As the protons are added one by

one, the electrons fill up hydrogen-one, the electrons fill up hydrogen-like orbitals.like orbitals.

Fill up in order of energyFill up in order of energy

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Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s7s

2p

3p

4p

5p6p

3d

4d

5d

7p6d

4f

5f6f

Orbitals available to a Hydrogen atom

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Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

With more electrons, repulsion changes the energy of the orbitals.

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Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

He with 2 electrons

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Incr

easi

ng e

nerg

y

1s

2s

3s

4s

5s6s

7s

2p

3p

4p

5p

6p

3d

4d

5d

7p 6d

4f

5f

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DetailsDetails Valence electronsValence electrons- the electrons in - the electrons in

the outermost energy levels (not d).the outermost energy levels (not d). Core electronsCore electrons- the inner electrons- the inner electrons Hund’s RuleHund’s Rule- The lowest energy - The lowest energy

configuration for an atom is the one configuration for an atom is the one have the maximum number of have the maximum number of unpaired unpaired electrons in the orbital.electrons in the orbital.

C 1sC 1s2 2 2s2s22 2p 2p22

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DetailsDetails Elements in the same column have the Elements in the same column have the

same electron configuration.same electron configuration. Put in columns because of similar Put in columns because of similar

properties.properties. Similar properties because of electron Similar properties because of electron

configuration.configuration. Noble gases have filled energy levels.Noble gases have filled energy levels. Transition metals are filling the d Transition metals are filling the d

orbitalsorbitals

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The ShorthandThe Shorthand Write the symbol of the noble gas Write the symbol of the noble gas

before the element before the element Then the rest of the electrons.Then the rest of the electrons. Aluminum - full configurationAluminum - full configuration 1s1s222s2s222p2p663s3s223p3p11

Ne is 1sNe is 1s222s2s222p2p66

so Al is [Ne] 3sso Al is [Ne] 3s223p3p11

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The ShorthandThe Shorthand

Sn- 50 electrons

The noble gas before it is Kr

[ Kr ]

Takes care of 36

Next 5s2

5s2Then 4d10

4d10Finally 5p2 5p2

[ Kr ] 5s24d10 5p2

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ExceptionsExceptions Cr = [Ar] 4sCr = [Ar] 4s11 3d 3d5 5

Mn = [Ar] 4sMn = [Ar] 4s22 3d 3d55

Half filled orbitals Half filled orbitals Scientists aren’t certain why it Scientists aren’t certain why it

happenshappens same for Cu [Ar] 4ssame for Cu [Ar] 4s113d3d1010

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Formation of IonsFormation of Ions Metals ALWAYS gain electronsMetals ALWAYS gain electrons

– Form cations (+) chargeForm cations (+) charge

Nonmetals ALWAYS lose electronsNonmetals ALWAYS lose electrons

– Form anions (-) ChargeForm anions (-) Charge

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Formation of IonsFormation of IonsGroups I and 2: Single ion formed is based Groups I and 2: Single ion formed is based

on the number of “s” electronson the number of “s” electrons

Transition Metals: Transition Metals:

First Ion = # “s’ electronsFirst Ion = # “s’ electrons

Second = # “s” electrons + 1Second = # “s” electrons + 1

P Sublevel Metals:P Sublevel Metals:

First Ion = # “p” electronsFirst Ion = # “p” electrons

Second Ion = # “p” + # “s” Second Ion = # “p” + # “s” electronselectrons