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Chapter 4 – Kathleen, George

The Development of a New Atomic Model


 * Electromagnetic Radiation-** Energy that shows wavelike behavior as it travels through space (i.e. radio waves, infrared light, x-rays, etc.).

=Electromagnetic Spectrum- The different forms of electromagnetic radiation, seen in the picture below.=


 * When less energy is present, there is a longer wavelength, and when more energy is present, there is a shorter wavelength.


 * All kinds of electromagnetic radiation move at the speed of 3.00 ´ 10­­8 (m/s) in space, and a slightly slower pace in matter.

=Wavelength- (l) The distant between two points on waves that are next to each other.=


 * Frequency-** The number of waves that pass a point each second.

Frequency and wavelength are directly related to each other. If frequency of light increases, then wavelength decreases, and vice versa. In the equation //c=////l////v, c//= the speed of light (3.00 ´ 10­­8 (m/s)), l = wavelength, and //v// = frequency. This equation is used to find the frequency or wavelength of a wave.


 * Example Problems**: The first problem’s work is shown as an example for the next two

93.7 Mhz __1,000,000__ hz = 93,700,000 hz 1 Mhz
 * Find the wavelength of a wave broadcasted by krock (93.7 Mhz).

3.00 ´ 10­­8 m/s = 93,700,000hz (l) __3.00__ __´__ __10­­8 m/s__ = 3.20m 93,700,000 First, you convert Mhz into hz, and then divide the speed of light by the frequency to get the desired answer.

Answer 4.12 x 1014 Hz
 * Calculate the frequency of a red light whose frequency is 728nm

Answer .0154m
 * Calculate the wavelength of a wave whose frequency is 1.9432 ´ 104


 * Photoelectric Effect-** When a metal gives off electrons as light is shined on it (demonstrated in the picture)
 * This is a demonstration of particle/wave duality, showing light with properties of a particle, releasing electrons.
 * There has to be a minimum frequency for the process to take place. If the frequency is below that minimum, it will not take place.


 * Quantum-** The minimum amount of energy that an atom can gain or lose.


 * Photon-** A particle of electromagnetic radiation that carries one quantum of energy, with no mass.
 * As indicated in the picture below, When an electron transfers from an energy level of high energy to an energy level of low energy, a photon is emitted.
 * When an electron transfers from an energy level of lower energy to an energy level of higher energy, the difference of energy between the two levels must be absorbed.


 * Ground State-** The lowest possible energy state of an atom**.**

possessed in the ground state.
 * Excited State-** A state at which the energy in the atom is a larger amount than is

The equation //E// = //hv// is used to find the energy of a wave. //E// is the energy or quantum (in joules), //h// is Planck’s constant, (6.626 ´ 10-34) and //v// is frequency.


 * Example Problems:**

102.5 Mhz __1,000,000__ Hz = (1.025 ´ 107)( 6.626 ´ 10-34) = 6.792 ´ 10-26 J 1Mhz
 * Find the energy of a wave whose frequency is 102.5 Mhz

Answer: 4.20 ´ 1017 1/s
 * Determine the frequency of a wave that has 2.782 ´ 10-16 J of energy

Answer: 1.908 ´ 10-13 J
 * Determine the energy of a wave whose wavelength is 1.04 pm


 * Line-emission Spectrum-** Particular frequencies that are given off by a particle when an electric current is passed through it, and is reflected through a prism


 * Continuous Spectrum-** Is a continuous range of frequencies, as seen in the picture, that are given off by visible light

The Quantum Model of the Atom

Vocabulary

__Orbital__- a three dimensional region around the nucleus that shoes the region in space where an election is most likely to be

__Quantum Number-__ specifies the properties of an atomic orbital and the properties of electrons in an orbital. - The first quantum numbers indicate the main energy level, shape and orientation - energy increases as distance from nucleus increases __Angular Momentum Quantum Number-__ indicates shape of orbital

Shape of Orbital s p d f Energy levels 1 3 5 7

__Magnetic Quantum Number-__ symbolized by m indicates orientation orbital around nucleus

Important Theories/Principles
 * HEISENBERG UNCERTAINTY PRINCIPLE- it is impossible to determine simultaneously the position and velocity of an electron or any other particle
 * QUANTUM THEORY- (Schrödinger) describes mathematically the wave properties of electrons and other particles.

Things to Remember- · Electrons have dual wave-particle nature · Quantization of electron energies is a natural outcome of the Schrödinger wave equation · Each orbital contains 2 electrons

Electron Configurations

Aufbau principle- an electron occupies the lowest energy orbital that can receive it

Pauli Exclusion Principle- no more than to electrons can occupy and orbital and they have to be spinning opposite ways

Hund’s rule- electrons distribute evenly before paring up at a particular energy level.

__Orbital Diagrams__

1. identify energy level for the atom 2. What types of orbitals can you have? 3. determine which orbitals are actually filled by using your periodic table 4. How many electrons do you have? 5. dram an orbital using boxes as orbitals and arrows as electrons
 * Remember that the number of boxes correlates with the number of possible orbital combinations in a different energy level (s -1, p-2…)

Examples:

1. Tell which one of A, B, C, or D is correct, and what element it is

Practice

Do orbital diagrams for 2. Sulfur 3. Iron

__Answers:__ - 3rd energy level - Fill s and p - 1s, 2s,2p,3s,3p - Have 16 electrons - S’s should have 1 box, P’s should have 3 - Every box should have 2 opposite spinning electrons except the last 2 of 3p - 4th energy level - Fill s, p, and d - 1s, 2s, 2p, 3s,3p, 4s, 3d - Have 26 electrons - S’s should have 1 box, P’s should have 3, D’s should have 5 - Every box should have 2 opposite spinning electrons except the last 4 of 3d
 * 1) B is correct, and it is oxygen
 * 2) Sulfur should
 * 1) Iron should

Noble Gas Configurations

-name the energy level appropriate letter -show how many electrons are in each energy block by writing it in superscript
 * 1) Starting with element, back up to the nearest noble gas
 * 2) write noble gas in brackets
 * 3) start with electron configuration after noble gas

Example – P [Ne] 3s2 3p3

You Try: - Bromine - Sodium

__Answers:__

Bromine [Ar] 4s2 3d10 4p5

Sodium [Ne] 2s1