1. Unit – Atomic Structure

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 Particles The atom of Nitrogen Location Charge
Mass(u)
Proton
Nucleus + 1
Neutron
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:Au ?
# p 6 79
# n 7 14
# e 8 MN 17
198 AN 11
Practice A#3

7. LecturePLUS Timberlake
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
Cl Cl – 37
AM= AM=
75.77 % %
Abundance: % of that isotope in nature
IMPORTANT: When the Atomic Mass of the isotope is not given, we can consider its Mass Number
AM =
Since their mass is different, they have diff physical properties such as BP.
LecturePLUS Timberlake

8. LecturePLUS Timberlake
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 C 14C
#P _______ _______ _______
#N _______ _______ _______
#E _______ _______ _______
LecturePLUS Timberlake

9. Relative Atomic Mass (no units!!!!!!!)
a)Find the relative atomic mass of Chlorine considering that the two isotopes occur in the ratio 3:1 b) Find the relative atomic mass of oxygen.

10. 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.

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

12. Radioactive Isotopes 60Co => 60 Ni + β
Many isotopes are radioactive once their nucleus breaks down spontaneously.
60Co => 60 Ni + β
I-131 and I-135 used as medical tracers
There are three forms of radiation:
Alpha - α
Beta - β or 0 e
Gamma - γ

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

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 1&2 Course Companion page 30.

17. Electromagnetic Spectrum
Electromagnetic waves can travel through space or matter.
The electromagnetic spectrum encompasses all possible wavelengths of radiation
The smaller the wavelength, the higher the frequency, the more energy the wave possesses.
Do question number 8 , IB M09(1)

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 λ has an associated frequency ν and energy E. These quantities are related according to the equations:
c = λ ν and E = h ν
Where
c ( speed of light ) = 3×108 m/s)
h (Planck's constant ) = × 10−34 J·s

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:
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.
The emission lines correspond to photons of discrete energies that are emitted when excited atomic states in the gas make transitions back to lower-lying levels.

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. Hydrogen Spectrum

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