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Chemistry PS1 2 Atomic Structure

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Activity: ELECTRON CONFIGURATION

Discover how we can determine elctron arrangements in atoms

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LAB Activities  follow safety guidelines above and in the activity
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Lab #5 Activity  Protons and Atomic #
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Atoms are tiny: FIND OUT HOW TINY movie Ted Talk

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Atoms have a a tiny, dense nucleus in the center--you saw how dense in the movie above.

The nucleus contains PROTONS (How many protons?  The number of protons in an atom = ATOMIC NUMBER of the element

Protons have a +1 charge and are equal in mass to neutrons which are also found in the nucleus (except in atoms of hydrogen-1)

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But atoms are neutral--have no overall charge because there are equal numbers of negatively charged electron in the atom.

ELECTRONS move around (not really orbiting) the nucleus. How many electrons in an atom?  The same as the number of protons--and equal to the atomic number of the element

Atom showing 4 electron shells:

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Start with the shell closest to the nucleus--count the electrons --here 2 (fill inner shells first--maximum number of electrons in Shell 1 = 2)

Shell #2 has 8 electrons (maximum number of electrons in Shell 2 = 8)

Shell number 3 has 8 electrons (maximum number of electrons in Shell 3 = 8)

There are no electrons in Shell 4

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For the electron arrangement: list the numbers in each shell, from Shell #1 outwards, with a comma between each

So electron arrangement =  2,  8,  8

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[There are a total of 18 electrons so this is the electron configuration of element number 18, argon

FLAME TESTS

Check out the flame test lab using water and the significance of the electron transitions which produce the different colors

Heat elevates electrons to higher energy levels--energy is ABSORBED--"excited" electrons.  When the energy is EMITTED, some energy wavelengths in the visible region.  Different elements produce different colors because they have different electron energy level transitions: 

               E =      hc

                     wavelength

h = Planck's constant

c = speed of light

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