the atomic nature of matter

8/17/2019 The Atomic Nature of Matter

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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

the atomic nature of matter

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