Part 3 : Lewis Dot Structures and Multiple Bonds
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Transcript of Part 3 : Lewis Dot Structures and Multiple Bonds
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Part 3: Lewis Dot Structures and Multiple Bonds
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Objectives• To learn how to depict covalent
bonds with Lewis Dot Structures• To understand the difference
between single, double, and triple covalent bonds
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H + H H2 + energy
atom atom molecule
Molecule has less energy and is more stable than atoms
Stability in Bonding
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Ways to represent the hydrogen molecule:
• H2 molecular formula - indicates number of atoms in molecule
• H-H structural formula - dash is 1 SHARED pair of electrons
• H:H dot structure (Lewis structure) - use 1 dot for each electron in highest energy level
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Covalent Bonding
• Covalent bonding is the sharing of electrons between atoms
• Because of this, the atomic orbitals of atoms overlap one another
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Crude picture representation: . . ATOMIC orbitals overlapping
Refined picture representation: . . MOLECULAR orbital -
holds 2 electrons maximum
Orbitals can not overlap completely because of the 2 nuclei
Orbital Overlap
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Lewis Dot Structures of Covalent Compounds
• Electrons of an atom are either core or valence electrons
• Valence electrons are the outermost and involved in chemical reactions
• They are shown in Lewis Dot structures
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• Valence electrons vary by element• Main Group element’s valence
electrons are equal to their group number
• Ex: Sodium (Na) belongs to Group 1A and therefore has 1 valence electron.HLi
KRbCs
NaBeMgCaSrBa
BAlGaInTi
CSiGeSnPb
NPAsSbBi
OSSeTePo
FClBrIAt
HeNeArKrXeRn
Transition metals
IA
IIA IIIA IVA VA VIA VIIA
VIIIA
Valence Electrons
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How many valence electrons does Potassium (K) have? 1
How many valence electrons does Antimony (Sb) have? 5
How many valence electrons does Phosphorus(P) have? 5
How many valence electrons does Magnesium (Mg) have? 2
Let’s Do It!!!
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HeNeArKrXeRn
VIIIA • Noble Gases in Group VIIIA have either two valence electrons (He) or eight (Ne, Ar, Kr, Xe, and Rn)
• They are extremely stable and this is the basis for the Octet Rule - elements react to attain the electron configuration of Group VIIIA
Noble Gases
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Neon has eight valence electrons, so its Lewis dot symbol is:
Ne
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• Remember metals on the left of the periodic table tend to lose electrons and nonmetals on the right tend to gain
• This is to achieve a stable configuration of 8 valence electrons
Octet Rule
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• Each fluorine atom has seven valence electrons and require one more electron to satisfy the Octet Rule.
F F
Covalent Bond
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F F• The left fluorine has a total of eight
electrons and the right fluorine has a total of eight valence electrons
• Nonmetallic elements react together and share electrons in order to obtain eight valence electrons
FF
Covalent Bond
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• The two electrons in the covalent bond are often represented by a line
• The F2 molecule can be represented using a line (bonding pair) and dots (six lone pairs)
FF
Covalent Bond
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• Some atoms have to share more than one electron in order to meet the Octet Rule
• Each oxygen atom has six valence electrons and they each require two more electrons to satisfy the Octet Rule
O O
Multiple Covalent Bonds
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• Both the left and right atoms now have a total of eight
• A double bond is represented by two single lines and each represents two electrons
O O
O O
Multiple Covalent Bonds
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• Hydrogen is an exception to the Octet Rule because it only needs two electrons to be stable
H F• H has one valence
electron and it requires one more
• F has seven valence electrons and it requires one more
H F
Covalent Bonds
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H F• The hydrogen atom now has a total of
two electrons around it and is stable• The fluorine atom now has a total of
eight electrons around it and is stable
Covalent Bonds
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Objectives• To learn how to depict covalent
bonds with Lewis Dot Structures• To understand the difference
between single, double, and triple covalent bonds
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