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Chapter 7 Atomic Structure and Periodicity

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Chapter 7Atomic Structure and Periodicity

7.1-7.2

7.3-7.4

7.5-7.8

7.9-7.11

7.13

- Electromagnetic radiation- the way energy travels through space.
- This energy travels at the speed of light.

- Three characteristics:
- 1.Wavelength
- 2.Frequency
- 3. Speed
- Wavelength =distance between two peaks (in meters)
- Frequency = number of waves per second (cycles per second)
- Speed= travels at speed of light (meters per second)

- Inverse relationship b/t. frequency and wavelength.
- Examples:

- Planck discovered:
- Energy is gained or lost in whole number quantities of hv
- Planck’s constant h = 6.626 x 10-34 J.s
- So Planck determined that energy is quantized (measured) in small packets called hv.

- Change in energy can be calculated by:
- Delta E = nhv
- n = intergers (1,2,3…)
- h = 6.626x10-34 J.s (Planck’s constant)
- v = frequency of EM radiation absorbed or emitted.

- Einstein viewed electromagnetic radiation as travelling in a stream of particles called “photons”
- E photon = hv= hc/lamda

- Energy is quantized. It occurs in units called quanta.
- Electromagnetic radiation exhibits wavelike properties and particulate properties also.

- EM radiation shows wavelike and particulate properties.
- Electrons exhibit particulate and wavelike properties.
- m = h/lamdav or lamda = h/mv
- Examples:

- Excited hydrogen atoms emit light!
- Hydrogen bonds are broken and H atoms release energy….
- Excess energy is released by emitting light of different wavelengths.

- Bohr proposed that an electron orbits the nucleus in a rigidly defined energy level.
Energy Atom = E photon = E e-final- E e-initial

- White light is a contiuous spectrum.
- The Hydrogen Emission Spectrum is a LINE spectrum
- Atoms in excited states exhibit line spectrum not continous spectrum.

E = -2.178 x 10-18(Z2/n2)

Z= nuclear charge

n = the size of the radius (the larger the value of n, the larger the orbit radius)

(-) sign means: energy of the electron bound to the nucleus is lower than if electron were at infinity.

At infinite distance, no interaction occurs and the energy is zero.