chemical bonds chemical bonding is the joining of atoms to form new substances
TRANSCRIPT
Chemical BondsChemical bonding is the joining of atoms to form new substances.
Most of the things you come in contact with are combinations of atoms
air water
milk
cotton
chocolatesugar
saltplastic
caffeine
wood
Valence ElectronsA valence electron is an electron in the outermost energy level of an atom, which causes bonding.
Valence Electrons
Carbon
4 valence electrons
Oxygen
6 valence electrons
Beryllium
2 valence electrons
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Valence Electrons• *Atoms of elements in Groups 1 and 2 have the
same number of valence electrons as their group number.
• *Atoms of elements in Group 3-12 do not have a general rule relating their valence electrons to their group number. However, they typically have between 1 or 2 valence electrons.
• *Atoms of elements in Groups 13-18 have 10 fewer valence electrons than their group number. (Exception - helium atoms have only 2 valence electrons, even though they are in group 18)
Octet RuleAtoms will combine to form compounds in order to reach eight electrons in their outer energy level.
The Octet Rule In Action
Notice how the sodium atom has one valence electron. It is this electron that it will try to
get rid of according to the Octet Rule.
Notice how this chlorine atom has seven valence electrons,
one away from eight. It will try to gain one more according to
the Octet Rule.
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Where do you think chlorine finds that one electron that it needs?
Pop Quiz Question #1Which shell is the valence shell?
A. FirstB. SecondC. MiddleD. Last
Pop Quiz Question #2Which element has 5 valence electrons?
A. chlorineB. nitrogenC. oxygenD. hydrogen
Writing Chemical FormulasA chemical formula uses chemical symbols to represent the atoms of the elements and the amount of each atom in a chemical combination
A subscript is a number written to the right of a chemical symbol and slightly below it. It tells how many atoms of each element are in the combination
Carbon dioxide carbon + oxygen
C + OCarbon dioxide
CO2 C + O + O
Pop Quiz Question #3
When sodium bonds with oxygen, they form
A. Na3O2
B. Na2O3
C. Na2O
D. NaO
Pop Quiz Question #4How many atoms are H2SO4?
A. 4B. 5C. 6D. 7
Types of Chemical Bonds
So, the prefix “co-” means . . .
What does the word cooperate mean?
Coworker?Co-captain?
The first type of chemical bond is called a covalent bond
Covalent bonds occur when atoms share electrons
share
COVALENT BOND
• Each pair of shared electrons creates a bond• Usually occurs between atoms of non-metals• Consequently, neither atom is "strong"
enough to steal electrons from the other, so they have to share electrons
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Types of chemical bonds
Ionic bonds occur when atoms transfer electrons
The second type of chemical bond is known as ionic bonds
Which different groups or families
of elements will most-likely
interact to create these
typesof bonds?
IONIC BONDS
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• The force of attraction between oppositely charged ions.• Usually form between atoms of metals and atoms of non-metals• Consequently, the non-metal is "stronger" than the metal, and can
steal electrons very easily from the metal.• Resulting compounds have a name that usually ends in –ide
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Covalent IonicCompounds Compounds
– Crystalline solids– High melting and
boiling points– Conduct electricity
when melted– Many are soluble in
water
– Gases, liquids, or solids– Low melting and
boiling points– Poor electrical
conductors– Most are not soluble in
water
Metallic Bond• A force of attraction between a positively
charged metal ion and the electrons in a metal• Many metal ions pass along many electrons• Many properties of metals, such as
conductivity, ductility, and malleability, result from the freely moving electrons in the metal
• Usually occurs between atoms of metals
Notice how the electrons do not just stay with one
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Pop Quiz Question #5
Which bond is formed from the transfer of electrons?
A. IonicB. CovalentC. Metallic