Chapter 4: Atomic Structure

1
Chapter 4 Atomic Structure

• 4.1 Studying Atoms p 100

2
Democritus

• Atoms philosopher

3
Aristotle

• No limit to division philosopher 4 elements

4
John Dalton

• Described elements, atoms, and compounds as pure
  substances

5
J.J. Thomson

• Positive and negative particles

6
Ernest Rutherford

• Gold Foil Experiment see p104 discovered
  positive nucleus atom is mostly empty space

7
Niels Bohr

• Energy levels orbits

8
Irwin Schrödinger

• Electron Cloud Model probability

9
James Chadwick

• The neutron

10
4.2 Structure of the Atom

• Rutherford had evidence for the existence of
  positive and negative sub-atomic particles and
  predicted a third type of particle by 1920.

11
Sub-atomic Particles

• Protons (p)
• positively charged
• found in the nucleus (center)
• charge of 1
• Electrons (e-)
• negatively charged
• found in the electron cloud
• charge of 1
• Neutrons (n0) 1932
• neutral particles
• found in the nucleus
• Tutorial Parts of the Atom

12
Comparing sub-atomic particles

• neutrons and protons are the same size and mass
• electrons are smaller and have much less mass
• Scientist do not have an instrument to see the
  parts of an atom. Everything we know about the
  nucleus and subatomic particles is based on how
  the particles behave (indirect evidence).

13
Atomic Number

• The number of protons defines the type of atom
• atomic number number of protons
• The whole number on the PT (p133)

14
hewgill.com/widgets/periodic-table-screenshot.jpg
15
Sample

• How many protons would any Helium atom have?
• In a neutral atom the positive protons balance
  out negative charge so
• Helium has ___ p and ____ e-

16
Mass Number

• The mass number (or atomic mass) gives the mass
  of an atom (in amu) round to nearest whole
  number
• mass number protons neutrons
• Why doesnt the mass include electrons?

17
What sub-atomic particles does Hydrogen have?
http//library.thinkquest.org/3616/chem/Periodic.h
tm
18
Practice

• If an atom has 13 protons and 14 neutrons, what
  is its mass number?
• What element is it?

19
Sodium?

• p
• n0
• e-

http//z.about.com/d/chemistry/1/0/2/Q/sodium.jpg
20
Mass Number Atomic Number
Number of Neutrons
21
Beryllium?

• p
• n0
• e-

http//www.periodictable.com/Elements/004/index.ht
ml
22
Isotopes

• atoms of the same element that have different
  numbers of neutrons (and mass)
• Example- every neutral carbon atom has ___
  protons and ___ electrons
• Most carbon have a mass of _____ , but some have
  a mass of 14 (12.011 is an average)
• Carbon-12 and Carbon-14

23
4.3 Modern Atomic Theory
24
Bohr Model

• nucleus surrounded by electrons that move in
  fixed orbits around the nucleus
• each electron has a specific amount of energy
  that can change if the atom loses/gains energy
• energy levels- amounts of energy an e- can have
• energy levels are
• like rungs on a ladder

25
Interesting Info

• movement of e- can result in a release of energy
• Heat produced by a explosion causes some
  electrons to move to higher energy levels, when
  they cool and move back to lower levels, they
  emit light

http//www.proteinpower.com/drmd_blog/?p173
26
Electron Cloud Model Schrödinger

• Bohr was correct that electrons have energy
  levels, but NOT CORRECT that they move in orderly
  orbits like the planets
• TODAY- scientist know that electrons move in a
  much less predictable way, they do not stay on a
  specific path
• We can mathematically describe the probability of
  where they are

27
Visualize an electron cloud

• Blades of a moving
• fan or propeller

http//universe-review.ca/I15-53-quantum.jpg
28
Orbital- shape of the cloud
-a region around a nucleus where an electron is
likely to be found -each energy level has a
certain number of orbitals and a certain number
of electrons it can hold -electron configuration
-the arrangement of electrons
http//phycomp.technion.ac.il/phr76ja/lecture1.ht
ml
29
Electron Configuration

• 1s2 2s2 2p6 3s2
• Coefficient energy level
• Letter orbital shape
• Superscript number of electrons
  located there
• What element does this configuration describe?