Atomic SpectrumMarch 11, 2015

Objectives

1. Explain why scientists know the identity of the chemical compositions of stars

2. Describe a flame test

3. Describe the Bohr model in terms of energy

Atoms can absorb and release energy

When atoms release energy they emit light

Each atom emits only a certain frequency of light

Shell(Bohr) model A region of space around the atomic

nucleus where electrons may be

Each shell can hold a limited amount of electrons

Series of seven shells accounts for the seven periods

Number of electrons held in each period is equal to the shell’s capacity for electrons

Valence Electrons Electrons in the outermost shell “combining

power”

Directly exposed to the external environment

The first to interact with other atoms

When electrons absorb energy they get excited and jump around

When jump back to the original position they release that energy as light

Flame Test

Na Li B Cu Ca

Spectroscope Observe color components of any light

source

Atomic Spectrum Light from atoms consist of a

number of individual frequencies

Pattern of frequencies of a particular element – atomic spectrum

White light separates into its color components by a prism

Each color corresponds to a different frequency of electromagnetic radiation

Atomic spectrum – atoms “finger print”

Emission – the frequencies the gas emitts Absorption – frequencies of all white light

EXCEPT those that are absorbed by the gas

•

Emission

Absorption

http://jersey.uoregon.edu/vlab/elements/Elements.html