bonding. electron configuration remember that electron configuration refers to the arrangement of...
TRANSCRIPT
Electron Configuration
• Remember that electron configuration refers to the arrangement of electrons in the orbital of an atom!
Three Types
We will study . . .Ionic Bonding
Covalent Bonding
Metallic Bonding
occurs between a metal and a nonmetal
occurs between two nonmetals
occurs WITHIN a metal sample
Chemical Bonding
• Compounds are formed from chemically bound atoms or ions.
• Bonding involves only the valence electrons.
• When atoms combine we call them molecules.
Valence Electrons• Electrons are found in specific
orbits/clouds spinning around the nucleus
• Valence electrons are the electrons located in the outermost orbit
Elements become stable when:
their outer orbit contains 8 electrons or their outer orbit becomes empty
Lewis Dot Diagrams show the # of Valence Electrons
Why are the noble gases unreactive?
The Octet RuleWhen the highest energy level of an atom is filled, the atom is stable.Atoms tend to gain, lose, or share electrons until they have eight valence electrons.Hydrogen and Helium are the only exceptions. Because they are so small, they are satisfied with two valence electrons.
Lewis Symbols / Electron Dot Diagram
Lewis symbols show the valence electrons as dots arranged around the atomic symbol.
hydrogen:
sodium:
chlorine:
Na
H
Cl
An oxidation number indicates how many electrons are lost or gained during the bonding process.
•Mg loses 2 electrons so it has an oxidation number of +2
•Oxygen gains 2 electrons
so it has an oxidation
number of –2.
Oxidation #
When Na loses that electron, its 2nd E.L. becomes full andstable with 8 e-.
Atoms with an electrical
charge are called ions.
Ionization•When an atom loses or gains electrons they become ions – or atoms with an electrical charge.
•If an atom LOSES an electron, it becomes an ion with a +1 charge.
•If an atom GAINS an electron, it becomes an ion with a –1 charge.
Chlorine has 7 valence electrons.
If Cl gains 1 electron, its valence shell will be full and stable.
Ionic Bonds
• form between a metal and a nonmetal• form as a result of a transfer of electrons
• Na becomes a positive ion =• Cl becomes a negative ion =• Cation means “to go down”
– also think cast off
• Anion means “to go up”– Also think accept
Na Cl
CationAnion
Ions Ions 1. Positively or negatively charged atoms. 2. (Number of protons not equal to the number of electrons.)3. Metals – give up electrons to form positive ions. (example: )4. Nonmetals – take in electrons to form negative ions. (example: )
Ionic Bonds
What is the formula for the compound that forms between magnesium and chlorine?
Cl
Mg
Cl
Ionic Compounds,Characteristic Properties
• High melting points• High boiling points
• Conduct electric current when melted and when dissolved in solution
• All of these properties are a result of the strong attraction among ions within the crystal lattice
Animated Reactionsodium and chlorine
• http://www.visionlearning.com/library/module_viewer.php?mid=55
• Youtube video of sodium reacting with chlorine
Covalent Bonding
Most atoms share electrons to gain an octet.
Covalent bonds are formed when e- are shared.
Polar Molecules• The type of atoms and
their shape determine if a molecule is polar or not
• With polar molecules there is an uneven distribution of charge…one atom has a stronger attraction for the electrons than the other
• Polar molecules attractions are stronger than nonpolar molecules
Polar Covalent Bonding
in a water molecule
• http://www.visionlearning.com/library/module_viewer.php?mid=55
Molecular Compounds,Characteristic Properties
• Low melting points• Low boiling points• Usually gases or liquids at room
temp.• Does not conduct electricity well• May or may not dissolve in water
(there are several types of molecular compounds)
Note the correct name
for a compound that
contains covalent bonds