Ch 9; Covalent Bonds Flashcards
Vocab: VSPER model
A model based on an arrangement that minimizes the repulsion of unshared pairs of electrons
Vocab: Exothermic
A chemical reaction in which more energy is released than is required to break bonds in the initial reaction
Vocab: Molecule
Forms when 2 or more atoms covalently bond
Vocab: Covalent bond
A bond that results from the sharing of valence electrons
Vocab: Pi bond
A bond that is formed when parallel p-orbitals overlap to share electrons
Vocab: Lewis structure
A model that uses electron dot structures to show how electrons are arranged in molecules
Vocab: Sigma bond
A single covalent bond that is formed when an electron pair is shared by the direct overlap of bonding orbitals
Vocab: Endothermic
A chemical reaction in which a greater amount of energy is required to break the existing bonds in the reactants than is released when the new bonds form in the product of molecules
Vocab: Resonance
Condition that occurs when more than 1 lewis structure exists for the same molecule
Vocab: Hybridization
The process by which the valence electrons of an atom are rearranged to form 4 new, identical hybrid orbitals
Steps for naming covalent bonds:
1) name the first element ( never use prefixes such as mono & never change end to -ide)
2) Use theprefixes to indicate # of atoms in formula
3) Name second element & change end to -ide if neccessary
4) Use prefixes to indicate # of atoms in formula
Steps for writing formulas for covalent compounds
1) Write symbol for the first element
2) Write subscript for element using any prefixes
3) Write symbol for second element
4) Write the subscript of the element using any prefixes
5) DO NOT REDUCE
Diatomic molecules
Molecules with 2 atoms of the same element
Richards Rule of 7’s
special diatomice molecules that naturally come in pairs
Common covalent compounds
H2O = water
NH3 = ammonia
CH4 = methane
C3H8 = propane
C4H10 = butane
C8H18 = octane
C2H5OH = Ethanol
Octet Rule
Atoms gain/lose/share electrons in order to obtain a full octet
Covalent bond:
Def: chemical bond resulting in the sharing of valence electrons
Non-metal with a non-metal bond
Bonding pair:
Pair of electrons shared, that belong to 2 atoms simulaneously
Sigma bond
First covalent bond in a double or triple bond
Unshared pairs
pair of valence electrons that do not participate in bonding
Properties of Covalent compounds
insulators, insoluable in water, low melting point, low boiling point, soft, molecules seperate easily
Properties of NETWORK covalent compounds
High melting point, high boiling point, electrical insulators, hard, insoluable in water
Bond Dissociation Energy (BDE)
Amount of energy required to break a specific covalent bond
Coordinate covalent bonds
When one atom contributes both bonding elevtrons to a single covalent bond
Lewis Structure steps
1) add the valence electrons for each atom in the chemical formula
2) Draw a skeleton structure using the first element in the formula
3) subtract 2 electrons per bond in the skeletron structure
4) Distribute the remaining electrons with four in total for each element (including the bonds)
5) is everyone happy?
6) If it is polyatomic (has an exponent) then place brackets
7) does it have resonance?
What happens when I run out of electrons?
Resonance: more than one valid lewis structure can be formed
Exeptions to the octet rule
Elements 1-5
Hydrogen (bonds once, Duet rule)
Helium (duet rule)
Litium (duet)
Beryllium (bonds twice)
Boron (bonds 3 times)
Hydrogen Bonding
“the boss” of intermolecular bonding, bonding of a covalently bonded hydrogen atom with an unshared electron pair
Why hydrogen?
Because its nuculeus is electron deficient when it bonds with an electromagnatie atom
Polarity of Molecules (steps)
1) draw the lewis structure
2) find the species type using the lewis structure
3) Find symmetry with VSEPR chart
Asymmetrical = polar covalant = no on the VSEPR chart
