Post on 04-Jan-2016
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Atoms, Ions, & IsotopesOh, My!Part III
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Outer Structure of an AtomOuter Structure of an Atom
• The electron cloud contains several energy levels
Electrons - negatively (-) charged particles located in specific energy levels surrounding the nucleus
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Outer Structure of an AtomOuter Structure of an Atom• Multiple energy levels in the electron cloud
completely surround the nucleus.Electrons follow a specific order to fill the energy
levels.
Maximum of 2
electrons
Nucleus
Maximum of 8
electrons Maximum of 8
electrons*
*Applies to the first 18 elements only
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Valence Electrons•Electrons found on the last/outermost energy level
•The number of valence electrons determines reactivity of the atom
•Full outer shell-Nonreactive•As you get closer to a full shell the less reactive an atoms is
–Atoms can achieve a full shell by losing or gaining electrons
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This is the order the electrons fill up the energy levels/shells/orbitals.
You do not go to the next energy level until the one you are on is full.
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Charge of an Atom•Most atoms are NEUTRAL (no charge)
The number of Protons = number of Electrons
•If an atom loses or gains electrons then it will have a charge
#p > #e; positive charge#p < #e; negative charge
•The valence electrons are the electrons being lost or gained.
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Cation•Positively charged ions•#p > #e•Lost of electron(s)
IonsAn atom that has gained or lost electrons
In the example, sodium is a neutral atom when it has 11 protons and 11 electrons.
When it loses its one valence electron, it has 11 protons and 10 electrons, which makes it have a +1 charge.
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• Negatively charged ions• #p < #e• Gain electron(s)
Anion
In the example, chlorine is a neutral atom when it has 17 protons and 17 electrons.
When it gains one electron, it has 17 protons and 18 electrons, which makes it have a -1 charge.