the atomic nature of matter
TRANSCRIPT
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Chapter 11
The Atomic
Nature of
Matter
(where & collide...)Physics
Chemist ry
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Matter The Atomic Hypothesis
The idea of matter:
● First thought by Aristotle to be a combination of
four elements — earth, air, fire, and water ● Thought to be composed of atoms by Greeks
from the fifth century BC
● The term 'atomos' was coined by Democritus !tmeant 'uncuttable' or "the smallest indi#isible
particle of matter"
● Is this still true today?
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The Atomic Hypothesis
● Further proposed as atoms in $%&&s by
meteorologist and schoolteacher John Dalton
● !n $%'(, Robert Brown, a botanist, obser#edcollisions between #isible particles and in#isible
atoms )Brownian motion* — later confirmed by
Albert Einstein as e#idence for
the e+istence of atoms
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Characteristics of Atoms
i!e main "oints of Dalton's atomic theory:
$ lements are made of e+tremely small particles called atoms
' Atoms of a gi#en element are identical in si-e, mass, andother properties. atoms of different elements differ in si-e,
mass, and other properties
/ Atoms cannot be subdi#ided, created, or destroyed
0 Atoms of different elements combine in simple whole1numberratios to form chemical compounds
2 !n chemical reactions, atoms are combined, separated, or
rearranged
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Atoms
#All thin$s are made of atoms%little "articles
that mo!e around in "er"etual motion&
attractin$ each other when they are a littledistance a"art& but re"ellin$ u"on bein$
suee(ed into one another)*
% Richard eynman
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Characteristics of Atoms
+haracteristics of atoms:
$ Atoms are incredibly tiny 3 Angstrom )$&1$& m* scale
' Atoms are numerous 3 A#ogadro"s number/ Atoms are perpetually in motion 3 Brownian motion
0 Atoms are ageless
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Atomic Imagery
4 Atoms are too small to be
seen with the naked human
eye
4 The human eye will respond
to wa#elengths about /5& to
(&& nm 3 this is the spectrum
of #isible light
4 These wa#elengths are too
big to #iew the much smaller
si-e of a typical atom
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Atomic Imagery
,ow to !iew atoms)))
4 6o atoms must be #iewed using something smaller
than the si-e of an atom 3 electrons4 Atoms, as well as other small
ob7ects may be #iewed today
using electron microscopy
4 To the right is one of the firstscanning electron micrograph
images showing chains of
indi#idual thorium atoms
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Atomic Imagery
4 !n the mid1$5%&s e#en better images of atoms came with
the ad#ent of the scanning tunneling microscope
4 The picture below shows an image of 0% iron atoms
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Atomic Structure
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Atomic Structure
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Atomic Imagery
Different -inds of electron microsco"es:
4 .E/ 3 scanning electron microscope
4 .T/ 3 scanning tunneling microscope4 TE/ 3 transmission electron
microscope
4 .TE/ 3 scanning transmissionelectron microscope
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Atomic Structure
The Atomic .tructure is com"osed of:
● an atomic nucleus
3 contains most of the atom8s mass
3 comprised of either positi#e or neutral nucleons which all ha#e the same mass
• 9ositi#e nucleons are called "rotons
• :eutral nucleons are called neutrons
● electrons 3 #ery small and #ery fast negati#ely charged
particles that orbit around the nucleus
3 determine the atom8s si(e
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The Elements
.im"lified /odel of the Atom
● Atoms can be represented as ha#ing different layers or
0 shells1 where electrons reside
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The Elements
Elements
● are pure substances composed of only one kind of atom
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The Elements
ocusin$ on +arbon
4 Carbon is a #ery common element that can take many
forms and is found in a lot of li#ing things )or organic
matter
4 ,ere are some common forms that carbon can ta-e:
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The Elements
Buc-minsterfullerene or 0buc-y balls1
4 Bucky balls are ;& carbon atoms in a #ery
specific, geometric, spherical form
4They can also be takenapart, flattened and turned
into different types of carbon
nanotubes<
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HeHelium
4.003
2
The Periodic Table of Elements
4 lements are classified by the number of protons in their
nucleus 3 their atomic number
4 The mass number is the total number of nucleons )protons
and neutrons* in an atom8s nucleus
4 The total mass of a single atom is called its atomic mass
They are measured in atomic mass units or amu
H
e
4
2
Elementname
Atomicmass
Elementsymol
Atomicnumer
Massnumer
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The Periodic Table of Elements
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Periodic Table of the Elements
The 2eriodic table is3
4 a chart )chemist8s road map* of elements arranged
by atomic number
4 classified by the number of "rotons in the nucleus
4 arranged from left to ri$ht
4 each ha#ing one more "roton and electron than thepreceding element
4 The elements on the far right ha#e their outmost
electron shells filled to ca"acity and they are known
as the 4oble $ases
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Relative Sizes of Atoms
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Relative Sizes of Atoms
Diameters of the outer electron shells:
4 are determined by the amount of electrical char$e in the
nucleus
4 gradually decrease from left to ri$ht across the periodic
table
4 But the diameter increases from top to bottom down the
periodic table
● As nuclear charge increases and electrons are
added to outer orbits, the inner orbit shrinks
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Ions and Isotopes
An ion is a charged atom
= A positi#e ion has deficiency of electrons 3 cation
= A negati#e ion has an e5cess of electrons 3 anion
= The number of protons in nucleus matches the
number of electrons around nucleus for a electricallystable atom, but not necessarily the number of
neutrons
E5am"le: >ithium )>i* has / electrons and / protons,but 0 neutrons
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Isotopes
Isoto"es:
4 Atoms of the same element with a different number of
neutrons
4 !sotopes may show identical beha#ior to their original
element
4!dentified by their mass number )total number of protonsand neutrons in the nucleus or number of nucleons*
+ample? !ron isotope with '; protons contain /& neutrons@ass number is number 2;, referred to as iron1
2;
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Isotopes
4 Deuterium is an isotope of the element ydrogen
with 7ust one additional neutron
4 !t is used to make ‘heavy water’ ,D2 O instead of ' !t8s e+tra
neutrons are used for cooling down
nuclear power plants
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olecules
/olecules
3 Two or more atoms bonded together
+ample?
• :/ )ammonia*
• / atoms of hydrogen and $ atom of nitrogen
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Compounds and i!tures
● hen atoms of different elements bond to one another,they make a compound "
● A compound is different from the elements from which it ismade
● !t can only be separated into its constituent elements by
chemical means
+ample? Table salt 3 a compound of
sodium ):a* and chlorine )Cl*
#aCl
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Compounds and i!tures
● Two or more substances that are mi+ed together withoutchemically bonding is called a mixture"
+ample? Air )a mi+ture of se#eral gases*
● Two or more substances thatare mi+ed together withoutchemically bonding is called amixture"
+ample?
Dool1Aid #s 9arfait
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Antimatter
/atter
4 Composed of atoms with positi#e nuclei and ne$ati!e
electrons
Antimatter
4 Composed of atoms with negati#e nuclei and "ositi!e
electrons )positrons*
4 2ositrons 3 ha#e the same mass as an electronbut are positi#ely charged
4 Anti6"rotons 3 ha#e the same mass as protons
but are negati#ely charged
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Antimatter
Antimatter
4 Both matter and antimatter cannot e+ist in our en#ironment
4 !f matter and antimatter +788IDE , only E9A8 amounts
will annihilate each other in a B>A6T F EA!A:T
:EG