Structure of the Atom Atomic Theory - PowerPoint PPT Presentation

1 / 65
About This Presentation
Title:

Structure of the Atom Atomic Theory

Description:

Structure of the Atom Atomic Theory Spectra of some elements THE END * * * * * * * * * * * * Different E levels hold different # s of e- E level 1 = 2 e- E level 2 ... – PowerPoint PPT presentation

Number of Views:2243
Avg rating:3.0/5.0
Slides: 66
Provided by: AHS70
Category:

less

Transcript and Presenter's Notes

Title: Structure of the Atom Atomic Theory


1
Structure of the Atom Atomic Theory
2
AlchemyB.C.
  • Before there were chemists, alchemists studied
    matter in an effort to make gold from other
    metals.

3
Leucippus Democritus460 - 370 BC
  • Atomists Theory of Matter
  • Matter is made of invisible, pebble like
    particles called atoms.
  • Like pieces of a mosaic
  • BUT this was not backed by experimental evidence
  • Godless

4
Aristotle384 - 322 B.C.
  • Believed that matter was composed of 4 elements
  • Earth
  • Air
  • Fire
  • Water
  • Spiritual elements

5
Epicurius341 - 270 BC
  • Opposed Aristotle Plato teachings
  • Tried again to bring the Atomists theory to the
    forefront
  • Denied
  • . . . and the Dark Ages ensued

6
Daltons Atomic Theory (early 1800s)
  • 1. All elements are composed of atoms
  • atoms are indestructible cant be changed
  • 2. All atoms of an element are exactly alike
  • 3. Atoms of different elements have
    different masses
  • 4. Compounds are formed by joining two or more
    elements in whole number ratios

7
Thomson and the Cathode Ray Tube(late 1800s)
  • Thomson concluded that the atom was made of
    smaller particles.
  • Discovered particles with negative charge
  • Electron
  • No matter what metals were used they all produced
    electrons
  • Therefore all elements (atoms) contain electrons

8
(No Transcript)
9
  • Soon after Thomsons discovery of the electron,
    the proton was discovered, SO
  • Thomson theorized a new model of the atom.

10
Rutherfords Gold Foil Experiment
11
charge
charge
12
Rutherfords Gold Foil Experiment
13
Rutherfords Model (early 1900s)
Experiments with alpha particles
  • OBSERVATIONS
  • most ? particles went straight through
  • few ? particles were deflected or bounced back
  • CONCLUSIONS
  • atoms are mostly empty space
  • few ? particles came close to or hit a positive
    particle in the atom

14
Rutherfords Planetary Model
  • Electrons orbit a large, positive nucleus
  • Electrons emit energy as they fall toward the
    nucleus

15
Bohr Model of the Atom(early 1900s)
  • Electrons have definite, fixed orbits
  • Electrons have a definite energy
  • orbits farther from the nucleus have greater
    energy

16
Orbital 2
Orbital 1
energy level shell orbital
17
Electron-cloud model Wave-mechanical
modelQuantum . . . Model Modern Model
18
Basic Atomic Structure
19
Atoms are not solid spheres, they are composed of
. . . Subatomic particles
  • Electron e-
  • found outside the nucleus in orbitals
  • Proton p
  • found inside nucleus
  • Neutron n0
  • found inside nucleus

20
Atomic Number
The number of protons defines the element
  • Each element has a different atomic number 1, 2,
    3, 4, 5, 6, 7, 8, 9, 10 . . .
  • The atomic number is equal to the number of
    protons

21
(No Transcript)
22
Mass Numbera.k.a. Atomic Mass
  • the mass of the atom is contained in the nucleus
  • Masses of electrons are negligible
  • it takes 1836 e- to equal the mass of 1p
    or 1no

23
  • atomic mass p no
  • 1 p 1 amu or 1/12 the mass of C atom
  • 1 no 1 amu or 1/12 the mass of C atom

Carbon - 12 is the standard that all masses are
compared to. All other elements have relative
masses
24
  • How do you determine the number of neutrons in an
    atom?
  • How do your determine the number of electrons in
    an atom?

Atoms are neutral
25
Atoms of the same element are not necessarily
alike . . .
Same atomic number different mass number
26
(No Transcript)
27
Isotopic Notation
  • How many protons?
  • How many neutrons?

a.k.a. H-1
28
Isotopic Notation
  • How many protons?
  • How many neutrons?

a.k.a. H-2
29
Isotopic Notation
  • How many protons?
  • How many neutrons?

a.k.a. H-3
30
How is atomic mass calculated?
  • Mass p no
  • BUT since the number of neutrons in an atom can
    vary . . .
  • Mass H 1 Mass H 2 Mass H 3
  • The atomic mass is an AVERAGE mass of the
    isotopes
  • BUT!!!!!! Is the mass of Hydrogen is 1.00794 and
    not 2???????

31
Weighted average
  • Test grades 50
  • HW 10
  • Labs 40
  • Test avg 85
  • HW avg 90
  • Lab avg 75

What is your MP average?
32
Average atomic mass of H
  • H-1 99.99
  • H-2 .01
  • 1amu x .9999 .9999
  • 2amu x .0001 .0002

1.0001
Do NOT use division in a weighted average!!!!
33
Electron Configurations
34
Different E levels hold different s of e-
  • E level 1 2 e-
  • E level 2 8 e-
  • E level 3 18 e-
  • E level 4 32 e-

But NEVER more than 8 outermost
35
You can tell an atoms electron configuration
based on its location in the periodic table
36
Electron Configuration
12.0111 C 6 2 - 4
37
Practice Problems
  • What is the electron configuration of potassium?
  • 2-8-8-1
  • How many electrons does Phosphorus have in its
    2nd E level?
  • 8
  • How many e- does sodium have in its first
    orbital?
  • 2
  • How many e- does iron have in its 3rd E shell?
  • 14

38
e- in higher E levels have more E
39
Valence electrons
  • Outermost number of electrons
  • Never more than eight
  • Highest energy

40
How many valence electrons?
  • hydrogen
  • potassium
  • Sodium
  • Lithium
  • Magnesium
  • Calcuim
  • Barium
  • Fluorine
  • chlorine
  • Neon
  • Argon
  • Krypton

41
Notice anything?
  • Elements (atoms) in the same group have the
    same number of valence e-
  • The of valence e- corresponds to the last digit
    of the group number

42
Lewis Dot Structure
  • Method of showing valence electrons
  • Never more than 8 total

Symbol represents the kernel Dots show valence
electrons
43
Draw Lewis Dot diagrams
  • lithium
  • beryllium
  • fluorine
  • argon
  • phosphorus
  • sodium
  • helium

44
Ions
45
Ions are particles that carry a charge
  • The charge an ion carries is the DIFFERENCE
    between the p and e-

46
(No Transcript)
47
  • Ions form because atoms want to have a full outer
    energy level.
  • Want an electron configuration like the nearest
    noble gas.
  • They will do this the easiest way possible.
  • Na loses 1 electron Na1
  • Cl gains 1 electron Cl-1

48
(No Transcript)
49
Practice Problems
  • What is the charge on an ion with 7p and 5e- ?
  • What is the charge on an ion with an atomic
    number of 8 and 5e-?
  • What is the charge on an ion with an atomic mass
    of 35 if this atom has 18 neutrons and 18
    electrons?

50
Draw Lewis Dot diagrams
  • Cl -
  • Ca 2
  • Lithium ion
  • Beryllium ion
  • Fluoride ion
  • Phosphide ion
  • Oxide ion

51
Electron Orbital Notation
  • e- dont actually zoom around the nucleus on
    little electron highways as seen in the Bohr
    Model of the Atom.
  • THEREFORE
  • true electron configuration isnt that easy!

52
  • Each principle orbital 1, 2, 3, 4 . . . is
    divided into suborbitals s,p,d f
  • These are some shapes of the orbitals

53
  • s can hold 2 electrons
  • p can hold 6 electrons
  • d can hold 10 electrons
  • The size of the suborbital is the same for any
    one energy level
  • 3s, 3p, 3d are the same size
  • 4s, 4p 4d are the same size but larger than the
    3s

54
  • When writing orbital notation
  • Orbital Suborbital of electrons
  • or
  • level sublevel number (oh my!)

55
(No Transcript)
56
Ground State vs. Excited state
  • So far weve discussed e- in their ground state

57
Ground State e-
  • Definition e- occupy lowest possible energy
    levels
  • Most stable electron configuration
  • The electron configurations on your periodic
    table show e- in their ground state
  • ex. 2 - 8 - 6

58
Excited State e-
  • Definition e- of an atom occupy higher E levels
    when lower E levels are still vacant
  • ex. 2 - 7 - 7
  • ex. 2 - 3 - 1

Can hold up to 8 here.
Can hold up to 8 here.
59
Ground state 2 - 6Excited state 2 - 5 - 1
60
Ground State to Excited State
61
Excited State to Ground State
62
Spectroscopy
  • Emission lines of elements
  • Bright line spectra

63
  • If you hold a prism to light you will see a
    continuous spectrum of color.
  • ROYGBIV

64
(No Transcript)
65
Emission lines
  • Visible light produced by electrons are confined
    to narrow lines of color called bright line
    spectra.
  • These emission lines are used to identify
    elements
  • fingerprints

66
Spectra of some elements
67
THE END
Write a Comment
User Comments (0)
About PowerShow.com