What’s it all about?. The Basic Atom Smallest particle of an element that still has the...
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Atomic Structure, The Periodic Table & Atomic Theory What’s it all about?
What’s it all about?. The Basic Atom Smallest particle of an element that still has the element’s properties Atomic Theory explains what atoms look like,
The Basic Atom Smallest particle of an element that still has
the elements properties Atomic Theory explains what atoms look
like, and how and why they behave the way they do Democritus (400
BC) proposed the existence of atoms (philosophy) John Dalton (1800)
was the first to have scientific evidence to support this
Considered the Father of Modern Atomic Theory
Slide 3
Daltons Atomic Theory Daltons experiments showed him several
things about the existence of atoms he had 5 postulates All matter
is made of atoms Atoms are small, indestructible spheres Atoms of
the same element are identical Atoms always combine in compounds in
whole number ratios In chemical reactions atoms are combined,
separated or rearranged
Slide 4
Daltons Model Daltons idea of the atom was a small sphere hence
The Marble Model
Slide 5
Current model building blocks of matter Charge: Neutral (no
charge) particles made up of 3 subatomic particles in 2 regions
Electron Cloud: Diffuse (spread out very thinly) Negatively charged
area outside of the nucleus Electrons (e - ): o each has a (-1)
charge o little mass (0 amu) o located outside of the nucleus
Nucleus Tiny Positively charged Dense mass in the atoms center has
2 particles (p + ) protons o each has a (+1) charge o has a mass of
1 a.m.u.* (n) Neutrons o no charge o has a mass of 1 a.m.u.*
*a.m.u. = atomic mass unit
Slide 6
- 0 Region & Particle Relationship Atoms Electron Cloud
Charge Balance Subatomic Particle Region Charge Nucleus Neutron
Proton electron +
Slide 7
The Electron
Slide 8
The Electron Fun Facts Abbreviated e - Gives the electron cloud
its charge Gives the element its chemical properties Structure:
Lepton (fundamental particle not made of smaller particles) Mass =
0 amu* (amu = atomic mass unit) Not really 0 but 1/1200-1/2000 th
the mass of a proton) Charge: negative (exactly balances the p +
positive charge) Location: Electron Cloud
Slide 9
The Electron on the Periodic Table How many electrons are there
in an element?? Where do you find it??? 20 Ca Calcium 40.078 # of e
- = Atomic Number but only in a neutral atom Lets make a note on
our PT & test each other
Slide 10
The Electron History/Theory Discovery #: 1 st subatomic
particle discovered Discovered by JJ Thomson in 1897 JJ Made a CRT
(cathode ray tube) and found that when he shot electricity through
it a beam of light appeared The beam of light was affected by
magnetic & electric forces (does light do that??) He proposed
that it wasnt light but tiny, negatively charged particles he
called electrons (btw: he thought the discovery was useless)
Slide 11
Thomsons Model The atom was Neutral in charge so Most of the
atom was a diffuse positively charged goo or matrix Electrons were
tiny particles that floated around in the goo. Electrons were very
tiny compared to the mass of the atom
Slide 12
The Thomson Plum Pudding Model 1897 The Plum Pudding Model I
prefer the Chocolate Chip Cookie Dough Model negative electrons
positive matrix or goo that made up the rest of the atom
Slide 13
The Proton
Slide 14
The Proton Fun Facts Abbreviated p + Gives the nucleus a
positive charge Gives the element its unique characteristics &
identifies the element (# p + is unique to each element Structure:
Hadron (composite particle made of smaller particles) Mass = 1 amu*
Charge: Positive Location: Nucleus
Slide 15
The Proton on the Periodic Table How many protons are there in
an element?? Where do you find it??? 20 Ca Calcium 40.078 # of p +
= Atomic Number Lets make a note on our PT & test each
other
Slide 16
The Proton History/Theory Discovery #: 2 nd subatomic particle
discovered Discovered by Ernest Rutherford in 1918 Rutherford first
proposed the positive nucleus in 1911 from the Gold Foil Experiment
changing the model of the atom again
http://www.mhhe.com/physsci/chemistry/essentialch
emistry/flash/ruther14.swf
http://www.mhhe.com/physsci/chemistry/essentialch
emistry/flash/ruther14.swf
Slide 17
Rutherfords Models The nucleus was Very dense Had most of the
mass of the atom Was positive Very, very tiny compared to the
entire atom Atoms are mostly empty space The electrons move around
the outside of the nucleus Rutherford model nuclear model kind of
like a plasma ball w/ a tiny positive nucleus and electrons
floating around outside it Discovered the proton later in the first
nuclear reaction How tiny? 400 x tinier than this and thats only
the nucleus!!! Protons are smaller yet!!!!
Slide 18
The Rutherford (Nuclear) Models 1911 Model with just a positive
nucleus in the center of the electrons 1918 Model with protons
making up the nucleus
Slide 19
The Neutron
Slide 20
The Neutron Fun Facts Abbreviated n 0 Adds mass to the nucleus
Helps hold the nucleus together (prevents proton repulsion from
destroying the nucleus) Structure: Hadron (composite particle made
of smaller particles) Mass = 1 amu* Charge: Neutral (no charge)
Location: Nucleus
Slide 21
The Neutron on the Periodic Table How many neutrons are there
in an element?? Where do you find it??? 20 Ca Calcium 40.078 #n 0
is NOT found on the PT More on this later
Slide 22
The Neutron History/Theory Discovery #: 3 rd subatomic particle
discovered Discovered by James Chadwick (also a student of JJ
Thomson) in 1936 (Rutherford said it should be there, Chadwick gave
them evidence) Chadwick produced a beam of neutral particles that
knocked protons out of paraffin wax
https://www.youtube.com/watch?v=HnmEI94URK8 Led to the development
of the atomic bomb
Slide 23
Chadwicks Model Similar to the current model with p+ & n 0
in the nucleus and e- orbiting the nucleus in the electron
cloud
Slide 24
Isotopes & The Neutron
Slide 25
Isotopes & the Neutron Isotopes: Atoms of the same element
with different numbers of neutrons The number of neutrons can be
different in an element (thats why there is no neutron number on
the PT) The number of neutrons must be calculated for each isotope
Example: Magnesium has 3 isotopes Symbol#p + #n 0 #e - 12 Mg - 24
12 13 14 Mg - 25 Mg - 26
Slide 26
Isotopes & Mass Number Mass number (mass #) is the number
of p + & n o in a specific isotope of an element Mass # = #p +
+ n o or #n o = Mass # - #p + Lets put this on the PT
somewhere
Slide 27
Isotopes & Mass Number #1 How do you know which isotope you
have?? Mass # is found in one of 2 ways prioritized list 1.Isotope
Notation (given to you with the element symbol) 100% accurate C-14
Mass #Element Symbol So in C-14 there are 6 p + & 6 e - (atomic
number of C is 6) 8n 0 (Mass # - # p + = #n 0 or 14 - 6 = 8 ) OR 14
6 C Element Symbol Mass # Atomic #
Slide 28
Practice Isotope Notation Isotope Symbol # p + #n 0 #e - O-18
N-15 Si-30 Cl-37 K-41 Fe-54 Ni-62 Cu-65 Br-79 8108 787 141614
172017 192219 262826 283428 293629 354435
Slide 29
Isotopes & Mass Number #2 How do you know which isotope you
have?? 2. MCI (most common isotope) 50% accuracy Round the Average
Mass to a whole number to get mass # for the m.c.i.Average Mass 20
Ca Calcium 40.078 Average mass = 40.078 amu so. round it and The
mass number of the most common isotope is 40 so Ca-40 5 B Boron
10.806 Average mass = 10.806 amu so. round it and The mass number
of the most common isotope is 11 so B-11
Slide 30
Average Mass
Slide 31
Practice M.C.I. method Isotope Symbol # p + #n 0 #e - O N Si Cl
K Fe Ni Cu Br 888 - 16 (avg mass = 15.999) - 14 (avg mass = 14.006)
- 28 (avg mass = 28.084) - 56 (avg mass = 55.845) - 39 (avg mass =
39.098) - 35 (avg mass = 35.446) - 59 (avg mass = 58.693) - 64 (avg
mass = 63.546) - 80 (avg mass = 79.904) 777 141414 171817 192019
263026 283128 293529 354535
Slide 32
Sample Formats p+ n 0 p+ n 0 p+ n 0 Carbon - 12Carbon -
13Carbon - 14 6 6 6 6 78 Isotope Name Isotope Symbol # p+# n# e-
Lithium 6Li 6 Lithium 7Li 7 Iron Fe 28 Iron Fe-31 Chlorine Mercury
3 3 26 17 80 3 4 18 120 3 3 26 17 80 54 57 Cl - 35 Hg - 200
Slide 33
The Electron Cloud
Slide 34
Atomic Structure electron cloud The region of the atom around
the nucleus where the electrons are located Makes up most of the
atoms size Mostly empty space Made up of energy levels that e - can
move in and out of by absorbing & releasing energy e - absorb
energy and move to higher levels or release energy and drop back to
lower levels Nucleus 1 st Energy Level: holds up to 2 e - 2 nd
Energy Level: holds up to 8 e - 3 rd Energy Level: holds up to 18 e
- 4 th Energy Level: holds up to 32 e - Formula: ?? Skip valence e-
for now
Slide 35
Atomic Theory Electron Cloud Energy levels were proposed by
Neils Bohr in 1913 His data supported that e - absorb
heat/electrical energy & then release the energy as certain
colors of light He concluded that e - orbited the nucleus in energy
levels Jumped to higher levels when absorbing energy Released light
energy when they fell back down
https://www.youtube.com/watch?t=175&v=CUk 3enr-m0w
https://www.youtube.com/watch?t=175&v=CUk 3enr-m0w
Slide 36
Atomic Model Bohr Model Neils Bohrs model is sometimes called
the planetary model but we usually call it the Bohr Model light
released e.l. = 3 e.l. = 2 e.l. = 1 Time for a demo
Slide 37
Electron Cloud Later Discoveries In 1926 Erwin Schrodinger
& Max Born proposed that electrons actually behaved more like
waves than particles and therefore proposed the wave model.
Schrodinger is famous for his Schrodingers Cat example used to
explain this model The quantum mechanical model of the electron
cloud is our current model and many scientists have contributed to
its development. discovered e - exist within orbitals, which are
not circular, within the energy levelswhich are not circular dark,
shaded areas of the cloud are more likely to contain e -