Chapter 4

Arrangement of Electrons in AtomsChapter 4Section 4.1Wave-Particle Nature of Light 1. Electromagnetic Radiation -a form of energy that exhibits wavelike behavior as it travels through space

- moves at 3.0 x 1010 cm/s in a vacuum

- wavelength (): the distance between corresponding pointson adjacent waves - frequency (): the number of waves that pass a given point in a specific amount of time

- c = where: c is the speed of light 3.0 x 108 m/s is the wavelength is the frequency

- continuous spectrum: a spectrum in which all wavelengths within a given range are included

- electromagnetic spectrum: consists of all electromagnetic radiation, arranged according to increasing wavelength

2. Light as particles material does not burn a. glows red b. changes to yellow then white c. visible colors

photoelectric effect : the emission of electrons by certain metals when light shines on them

Quantum: a finite quantity of energy that can be gained or lost by an atom

Planck 1. proposed a relationship between a quantum of energy and the frequency of radiation 2. E = hv where: E = energy of radiation h = Planks constant 6.626 x 10-34 Js 3. photon: an individual quantum of light

4. ground state: state of lowest energy of an atom

5. excited state: a state in which it has a higher potential energy atom Ex. When atoms in a gaseous state are heated; the potential energy increases, return, give off the added energy in the electromagnetic radiation Ex. Continued: neon signs and fireworks

We can show this on different line spectrum or line-emission spectrum.

Each of the colored lines is produced by light of a different wavelength.

The different representative lines

Bohr Model 1. First model of the electron structure

2. Gives levels where an electron is most likely to be found

3. Incorrect today, but a key in understanding the atomSection 4.2Quantum Model of the Atom 1. Describes mathematically the wave properties of electrons and other very small particles

2. dual wave-particle nature of light

3. orbital: a three-dimensional region about the nucleus in which a particular electron can be located

Review characteristics of electrons 1. extremely small mass 2. located outside the nucleus 3. moving at extremely high speeds in a sphere 4. have specific energy levels 5. when atoms are heated: bright lines appear 6. arranged in discrete levels 7. absorbs energy to jump: to a higher energy level 8. falls to a lower level, energy is emitted9.

gain loss of energy of energy Electron levels (shells)Contain electrons that are similar in energy and distance from nucleusLow energy electrons are closest to the nucleusIdentify by numbers 1,2,3,4,5,6The first shell (1) is lowest in energy, 2nd level is next 1