Physical SciencePhysical Science

Ch. 18Ch. 18

Section 1Section 1

Structure of the AtomStructure of the Atom

Structure of the AtomStructure of the Atom• ElementElement

–Matter that is composed of Matter that is composed of one type of atom.one type of atom.

• AtomAtom–The smallest particle of The smallest particle of

matter that retains the matter that retains the property of the elementproperty of the element

• ProtonProton–Has positive chargeHas positive charge–Located in nucleusLocated in nucleus

• NeutronNeutron–Has neutral (no) chargeHas neutral (no) charge–Located in nucleusLocated in nucleus

• ElectronElectron–Has a negative chargeHas a negative charge–Located in electron cloudLocated in electron cloud

• QuarkQuark–What makes up protons and What makes up protons and

neutrons, what’s left overneutrons, what’s left over

Parts of an AtomParts of an Atom

How an atom looksHow an atom looks• NucleusNucleus

–contains proton & neutroncontains proton & neutron–Is positively chargedIs positively charged–Surrounded by electron cloudSurrounded by electron cloud

• Electron cloudElectron cloud–Contains electronsContains electrons–Is negatively chargedIs negatively charged

Changing Atomic TheoryChanging Atomic Theory

• DemocritusDemocritus–Atoms make up all Atoms make up all

substancessubstances• AristotleAristotle

–Matter was uniform Matter was uniform throughout, not composed throughout, not composed of smaller particlesof smaller particles

Changing Atomic TheoryChanging Atomic Theory• DaltonDalton

–11stst Proved that atoms exist Proved that atoms exist–Model was a simple sphereModel was a simple sphere

• Electron Cloud ModelElectron Cloud Model–Today’s accepted modelToday’s accepted model–Belief that nucleus (P&N) are Belief that nucleus (P&N) are

surrounded by “cloud” which surrounded by “cloud” which is the most likely region for is the most likely region for the electron to be located inthe electron to be located in

Electron Cloud ModelElectron Cloud Modelelectron

neutron

proton

Section 2Section 2

Masses of AtomsMasses of Atoms

Composition of Particles Composition of Particles within an Atomwithin an Atom

ParticleParticle Mass (g)Mass (g) ChargeCharge LocationLocation

ProtonProton 1.6726 x 101.6726 x 10-24-24 + 1+ 1 NucleusNucleus

NeutronNeutron 1.6749 x 101.6749 x 10-24-24 00 NucleusNucleus

ElectronElectron 9.1093 x 109.1093 x 10-28-28 -1-1 CloudCloud

The Masses of AtomsThe Masses of Atoms• Atomic NumberAtomic Number

–Number of protons in an atomNumber of protons in an atom–Allows element to be identified Allows element to be identified

by the number of protonsby the number of protons• Mass NumberMass Number

–Sum of protons and neutrons Sum of protons and neutrons within an atomwithin an atom

# neutrons = Mass # - Atomic ## neutrons = Mass # - Atomic #

• Atomic massAtomic mass–composed mostly of the composed mostly of the

protons and neutrons in the protons and neutrons in the nucleusnucleus

• Atomic Mass Unit (AMU)Atomic Mass Unit (AMU)–Unit of measurement for Unit of measurement for

atomic particlesatomic particles• Proton = 1 AMUProton = 1 AMU• Neutron = 1 AMUNeutron = 1 AMU• Electron = 1/1836 AMUElectron = 1/1836 AMU

• IsotopesIsotopes– atoms of the same element with different atoms of the same element with different

numbers of neutronsnumbers of neutrons• Different isotopes have different properties.Different isotopes have different properties.• Name of element followed by mass number Name of element followed by mass number

identifies the isotope.identifies the isotope.

• Average atomic massAverage atomic mass– weighted-average mass of an element’s weighted-average mass of an element’s

isotopesisotopes– closest to its most abundant isotope.closest to its most abundant isotope.

• When you round off the Atomic weight, When you round off the Atomic weight, you have the mass # (P + N) for that you have the mass # (P + N) for that element’s most common isotope element’s most common isotope

UraniumUranium238.03238.03

UU9292

Atomic Weight

Rounded gives the most common

isotopes mass #

#P + # N

Atomic Number

#P

So, to get the #N,

Atomic Weight

- Atomic Number

(#P + #N) – (#P)= # N

Section 3Section 3

Structure of the AtomStructure of the Atom

Periodic TablePeriodic Table• PeriodicPeriodic

– repeating according to some patternrepeating according to some pattern• Periodic TablePeriodic Table

– Arrangement of elements according Arrangement of elements according to some patternto some pattern

• Mendeleev – Father of ChemistryMendeleev – Father of Chemistry– devised the first periodic table based devised the first periodic table based

on atomic mass.on atomic mass.• MoseleyMoseley

– arranged the elements by atomic arranged the elements by atomic number rather than atomic massnumber rather than atomic mass• We use his arrangement todayWe use his arrangement today

• Groups or FamiliesGroups or Families–Vertical columns of elements Vertical columns of elements

with similar properties.with similar properties.• Elements in the same group Elements in the same group

have the same number of have the same number of electrons in their outer energy electrons in their outer energy level.level.

• PeriodsPeriods–horizontal rows of elementshorizontal rows of elements–They contain increasing numbers They contain increasing numbers

of protons and electrons.of protons and electrons.

• Elements are classifiedElements are classified–Metals (far left on table)Metals (far left on table)

–Nonmetals (far right)Nonmetals (far right)

–metalloids (semimetals)metalloids (semimetals)

• Synthesized elementsSynthesized elements–Man made elements created Man made elements created

in laboratories all over the in laboratories all over the worldworld

OrbitalsOrbitals

• 4 types of orbitals4 types of orbitalsS orbital S orbital (max of 2 e(max of 2 e--))

P orbital P orbital (max of 6 e(max of 6 e--))

D orbital D orbital (max of 10 e(max of 10 e--))

F orbital F orbital (max of 14 e(max of 14 e--))

Electron Dot DiagramElectron Dot Diagram

----- -- -XX- -- -

----

Electron Dot DiagramElectron Dot Diagram

----- -- -XX- -- -

----1

8

7

6

5

4

3

2

• 1s1s22

• 2s2s22 2p 2p66

• 3s3s22 3p 3p66 3d 3d1010

• 4s4s22 4p 4p66 4d 4d1010 4f 4f1414

• 5s5s22 5p 5p66 5d 5d1010 5f 5f1414

• 6s6s22 6p 6p66 6d 6d1010

• 7s7s22 7p 7p66

• 1s1s22

• 2s2s22 2p 2p66

• 3s3s22 3p 3p66 3d 3d1010

• 4s4s22 4p 4p66 4d 4d1010 4f 4f1414

• 5s5s22 5p 5p66 5d 5d1010 5f 5f1414

• 6s6s22 6p 6p66 6d 6d1010

• 7s7s22 7p 7p66

Valence ElectronsValence Electrons

ElectronsElectrons

in the outermost in the outermost energy levelenergy level

• 1s1s22

• 2s2s22 2p 2p66

• 3s3s22 3p 3p66 3d 3d1010

• 4s4s22 4p 4p66 4d 4d1010 4f 4f1414

• 5s5s22 5p 5p66 5d 5d1010 5f 5f1414

• 6s6s22 6p 6p66 6d 6d1010

• 7s7s22 7p 7p66

max 2max 2

max 8max 8

max 8max 8

max 8max 8

max 8max 8

max 8max 8

max 8max 8

Valence Valence ElectronsElectrons