Aim: How to distinguish electrons in the excited state

Do Now: Take out your homework. Compare your answers with the person next to you. If you have differing answers try to come up with a solution together.

What gives gas-filled lights their colors?

• An electric current passing through the gas in each glass tube makes the gas glow with its own characteristic color.

The Nature of Light• Light is a part of the electromagnetic spectrum radiant

energy composed of gamma rays, X-rays, ultraviolet light, visible light, etc.

• The energy of the electromagnetic spectrum moves through space as waves

Nature of Light• Sunlight consists of light with a continuous range of wavelengths

and frequencies. –When sunlight passes through a prism, the different frequencies

separate into a spectrum of colors.– In the visible spectrum, red light has the longest wavelength and

the lowest frequency.

Atomic Spectra• When atoms absorb energy, their electrons move to higher energy levels.

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

• The excitation fallback theory explains the visible emission (bright line) spectrum of element

• A ground state for the electrons in an atom is an energy state of lowest energy

• An excited state is an energy state of higher energy

• The amount of energy absorbed by the electron to go the excited state is equal to the amount released or emitted by the electron when it returns to the ground state.

Emission Spectrum

• A prism separates light into the colors it contains. White light produces a rainbow of colors.

Emission Spectrum• Light from a helium lamp produces discrete lines.

Excited hydrogen atoms emit a pinkish glow. When the visible portion of the emitted light is passed through a prism, it is separated into specific wavelengths that are part of the hydrogen’s line emission spectrum.

Emission Spectrum• The wavelengths of the spectral lines are characteristic of

the element, and they make up the atomic emission spectrum of the element.

• No two elements have the same emission spectrum.–The fingerprints of an element.

Emission Spectrum of a mixture of elements• The emission spectrum of a mixture of gases will be a combination of the individual gases in that mixture.

Energy of Light• Light can be described as a quanta, or packet, of energy that

behaves as if they were particles. Light quanta are called photons. The energy associated with a certain frequency of light is related by the equation:

• h = 6.63 X 10-34 Js

U DO IT NOW!

For the following configuration: 2-8-18-6

a) Identify the element.

b) Propose an excited state.

Simply add the electrons, which equal protons in a neutral atom, the atomic number.

2-8-18-6: 2+8+18+6 = 34 electrons indicates an atomic number of 34, which is Se

Write a configuration with the same number of electrons as the ground state , but with a different configuration.

2-8-18-6(ground): 2-8-17-7 (excited)♫NOTE – electrons furthest from the nucleus are most likely to be excited (promoted).