lecture 5.3- atomic spectra (honors)

Bellwork- Groups

Draw a simple periodic table and label the following:a)Alkali metalsb)Alkaline earth metalsc)Halogensd)Noble gases e)Transition metals

Physics and the Quantum Mechanical Model

Neon advertising signs are formed from glass tubes bent in various shapes. An electric current passing through the gas in each glass tube makes the gas glow with its own characteristic color. You will learn why each gas glows with a specific color of light.

•The amplitude of a wave is the wave’s height from zero to the crest.

•The wavelength, , is the distance between the crests.

•The frequency,, is the number of wave cycles to pass a given point per unit of time.

is measured in hertz (Hz) = 1/s = s-1.

The wavelength and frequency of light are inversely proportional to each other.

The product of the frequency and wavelength always equals a constant

(c), the speed of light.

Light consists of electromagnetic waves.

•Electromagnetic radiation includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays.

• In a vacuum, all electromagnetic waves travel at the speed of light (c).

•c = 2.998 108 m/s

The electromagnetic spectrum consists of radiation over a broad band of wavelengths.

The Electromagnetic Spectrum

You must know the relative energies of the types of emr including the colors of visible light

Sample answers:

A. ultraviolet light:

Answer

C. visible light:

B. infrared light:

Give an example for each type of electromagnetic energy listed below.

Sample answers:

A. ultraviolet light:

Answer

the spectrum of lightwe see as color

C. visible light:

B. infrared light:

part of sunlight

radiant heat

When atoms absorb energy, electrons move into higher energy levels.

These electrons then lose energy by emitting light when they return to lower energy levels.

A prism separates light into the colors it contains. When white light passes through a prism, it produces a rainbow of colors.

When light from a helium lamp passes through a prism, discrete lines are produced.

The frequencies of light emitted by an element separate into discrete lines called the atomic emission spectrum of the element.

Mercury Nitrogen

In the Bohr model, the lone electron in the hydrogen atom can have only certain specific energies.

•When the electron has its lowest possible energy, the atom is in its ground state.

•Excitation of the electron by absorbing energy raises the atom from the ground state to an excited state.

•A quantum of light energy is emitted when the e- drops back to a lower energy level.

The light emitted by an electron moving from a higher to a lower energy level has a frequency directly proportional to the energy change of the electron.

The three groups of lines in the hydrogen spectrum correspond to the transition of electrons from higher energy levels to lower energy levels.

In 1905, Albert Einstein successfully explained experimental data by proposing that light could be described as quanta of energy.

• The quanta behave as if they were particles.

•Light quanta are called photons. A photon is a packet of light energy

The photoelectric effect describes how a photon of high enough frequency can cause an electron to be ejected from metals.

The electron absorbs the photon, if the photon is of a high enough frequency (energy) then the electron will pop off!

5.3 Section Quiz.

1. Calculate the frequency of a radar wave with a wavelength of 125 mm.

a. 2.40 109 Hz

b. 2.40 1024 Hz

c. 2.40 106 Hz

d. 2.40 102 Hz

5.3 Section Quiz.

2. The lines in the emission spectrum for an element are caused by

a. the movement of electrons from lower to higher energy levels.

b. the movement of electrons from higher to lower energy levels.

c. the electron configuration in the ground state.

d. the electron configuration of an atom.