Unit

1
Unit Atomic Structure
http//www.chemactive.com/ib_chemistry_HL
.html
2
The atom is the smallest particle of matter

• The atom of sodium can be identified by its
  number of protons!!!!!
• Look at the periodic table and find Na

3
Model of the Atom

• The atom of Nitrogen

• Particles

Location Charge Mass(u)
Proton Nucleus 1
Neutron Nucleus 0 1
Electron Orbits or Energy Levels _ 1/2000
4
Elemental Notation

• X

• AN- Atomic Number
• AN p e
• MN-Mass Number
• MN p n
• n MN - AN
• For example
• p
• e
• n
• 
  

5
Examples

• What would be the notation for the atom given?

6
Complete the following
C O Au ?
p 6 79
n 7 14
e 8
MN 17 198
AN 11
7
Isotopes

• Isotopes are atoms with the same number of
  protons, but different numbers of neutrons.
  Isotopes have identical chemical properties.
• Isotopes of Chlorine
• 35Cl 37Cl
• 17 17
• Cl - 35
  Cl 37
• AM34.968852
  AM36.965903
• 75.77
  24.23
• Abundance of that isotope in nature
• IMPORTANT When the Atomic Mass of the isotope is
  not given, we can consider its Mass Number
• AM

8
Exercise

• Naturally occurring carbon consists of three
  isotopes, 12C, 13C, and 14C. State the number of
  protons, neutrons, and electrons in each of these
  carbon atoms.
• 12C 13C 14C
• 6 6
  6
• P _______ _______
  _______
• N _______ _______
  _______
• E _______ _______
  _______

9
Relative Atomic Mass(no units!!!!!!!)

• a)Find the relative atomic mass of Chlorine
  considering that the two isotopes occur in the
  ratio 31
• b) Find the relative atomic mass of oxygen.

10
Properties of Isotopes

• Isotopes of the same element have identical
  chemical properties but may slightly differ in
  physical properties.

11
Radioactive Isotopeshttp//chemactive.com/flash_
spring/ib/use_of_radioisotopes.swfread SG page 7
and CC page 27

• Many isotopes are radioactive once their nucleus
  breaks down spontaneously.
• 60Co gt 60 Ni ß
• I-131 and I-135 used as medical tracers

• There are three forms of radiation
• Alpha - a
• Beta - ß or 0 e
• Gamma - ?

12
Carbon Dating

• The Qin Terracotta Warriors were discovered in
  China's province near in 1974 by six local
  farmers. A flurry of national media surrounded
  the discovery, and excavations were soon begun.
  The figures were found to be part of a massive
  burial complex whose construction was ordered by
  the First Emperor of China, Qin Shihuangdi, when
  he ascended the throne in 246 BC.
• Carbon dating with C-14 indicates that the
  ceiling was burned 2200 years ago.

13
Other Uses

• Radioactive isotopes can occur naturally or be
  created artificially.Their uses include nuclear
  power generation( U-235), crime detection,
  preservation of food,radiotherapy( Co-60) and
  treating and diagnosing illness( I-131).

14
Mass Spectrometer

• http//www.colby.edu/chemistry/OChem/demoindex.htm
  ltable
• http//www.magnet.fsu.edu/education/tutorials/java
  /massspectra/index.html

15

• This is an instrument used for measuring the
  exact masses of particles.
• It can be used on elements to determine the
  isotopic abundances and very accurate mass
  measurements or it can be used, on molecules to
  find out the nature of the molecule by looking at
  the fragmentation pattern of its destructive
  ionisation.
• It has several stages of operation that you must
  get famiiliar with (i.e. learn!)
• injection of the sample
• vaporisation of the sample (if it's not already
  gaseous)
• ionisation of the sample
• acceleration of the ions
• deflection of the ions
• detection of the ions

16

• The mass spectrometer is a device used to measure
  the mass of an atom by reading on a detecting
  screen the amount of deflection their 1 ions
  experience in a magnetic field the smaller the
  deflection the larger the mass.
• More specifically, the mass of an atom is
  measured by comparing its deflection in the mass
  spectrometer to the deflection of the carbon-12
  mass standard.
• For a sample of an element one can also count
  the number of atoms of each isotope that hit the
  detecting screen to obtain the fractional
  abundance of each isotope. The average atomic
  mass of the element that appears on the periodic
  table is then the weighted average of the isotope
  masses.
• zirconium-90 , 51.5
• zirconium-91 ,11.2
• zirconium-92, 17.1
• zirconium-94, 17.4
• zirconium-96, 2.8
• Do questions 12 Course Companion page 30.

17
Electromagnetic Spectrum

• Electromagnetic waves can travel through space or
  matter.
• The electromagnetic spectrum encompasses all
  possible wavelengths of radiation

18
Wave Properties of Matter

• Light or electromagnetic radiation may be viewed
  in one of two complementary ways as a wave or as
  a stream of particles
• Electromagnetic energy at a particular wavelength
  ? has an associated frequency ? and energy E.
  These quantities are related according to the
  equations
• c ? ? and
  E h ?
• Where
• c ( speed of light ) 3108 m/s)
• h (Planck's constant ) 6.626 10-34 Js
• http//csep10.phys.utk.edu/astr162/lect/light/wave
  s.html

19
Exercise

• Suppose we have an electromagnetic wave of
  wavelength 400nm.
• a)Calculate its frequency
• b)Calculate its energy
• c)
• 2. The yellow light given off by a sodium vapor
  lamp used for public lighting has a walength of
  589 nm.
• What is the frequency of radiation ?
• What is the amount of energy?

20
Spectra

• Dispersion is the basis for the prism and its
  ability to spatially separate light into its
  wavelengths
• http//csep10.phys.utk.edu/astr162/lect/light/disp
  ersion.html
• When radiation is separated into its different
  wavelengths, a spectrum is produced.

21

• Continuous spectrum Rainbow of colors containing
  light of all wavelengths.
• Emission spectra consists of a series of
  separate discrete lines, which become closer
  together(converge) towards the high energy end of
  the spectrum.

22
The Bohr Model of the Atom

• Proposal
• Electrons travel in orbits around the nucleus of
  the atom and each orbit is in a fixed energy
  level.
• In each case the wavelength of the emitted or
  absorbed light is exactly such that the photon
  carries the energy difference between the two
  orbits.

23
Electron Excitation

• http//www.upscale.utoronto.ca/GeneralInterest/Har
  rison/BohrModel/Flash/BohrModel.html

24
Hydrogen Spectrum
25

• The visible spectrum occurs when the electron
  falls to the second level.