Lewis and VSEPR Flashcards
Chemical bonds are found using ______
Valence electrons
An ionic bond is bond between a ____ and a _____
metal, nonmetal
Metals ____ an electron and become ____
lose, cations
become cations because they become more positive
nonmetals ____ electrons and become ____
gain, anions
become anions because they become negative
In NaCl sodium ___ an electron and chlorine ___ an electron
loses, gains
In NaCl when sodium loses an electron it becomes more ____ and when chlorine gains an electron it becomes more ____
positive, negative
This makes Na+ Cl-
What is a covalent bond?
Two or more nonmetals and hydrogen coming together to share electrons to fill their octets
In covalent bonding what to the shells do to share electrons?
the shells overlap
Is covalent bonding strong or weak?
Strong
In covalent bonding the radius (size) of the compound is _____ than the atomic radii
Smaller
In covalent bonding why is the radius (size) of the compound smaller than the atomic radii?
This is because of overlapping
What are the steps to drawing lewis structures?
- add up all the valence electrons for all the atoms in the molecules
- determine the central atom
- draw a temporary model using single bonds between atoms. Backfill remaining electrons from outside in filling octets as you go. Use double or triple bonds as needed
How do you determine the central atom in a lewis structure?
The one that can make the most bonds, the least electronegative.
Also, usually the atom that was written first is in the middle
How many valence electrons does C have?
4
How many valence electrons does N have?
5
How many valence electrons does oxygen have?
6
How many valence electrons does F have?
7
Why won’t hydrogen ever be in the center?
Because it can only form one bond
one bond = how many electrons?
2 electrons because electrons travel in pairs
What is a resonant structure?
When more than one structure could be drawn
When drawing a lewis structure if there is a negative how many valence electrons does that count as?
1 if it is just a negative on its own, if there is a number attached like 2 then it would add 2
Ex: CO3 2-
The total number of electrons is 24 (4 from carbon, 18 from oxygen, and 2 from the negative)
When drawing a lewis structure if there is a positive how many valence electrons does that count as?
The positive will actually take away electrons
it will take 1 away if it is just a + on its own and if its a + with a number attached it will take away the number attached to it
Ex: NH4+
(8 electrons: 5 from Nitrogen, 4 from Hydrogen, minus 1 from the positive)
What two elements will never have lone pairs?
Carbon and Hydrogen
The electron pair geometry is what ____ sees
electrons
molecular shape is what ___ see
we
How would you describe the linear?
Central atom with two things attached
CO2 is an example of linear
How would you describe trigonal planar?
central atoms with 3 things attached
BF3 and SO2 is an example of trigonal planar for the electron pair geometry
Why is the molecular shape of SO2 bent?
It is bent because Oxygen, Sulfur, and Selenium are group 16, this is the only group and the only 3 elements that will cause the molecular shape to be bent.
The Oxygen, Sulfur, and Selenium must be the central atom in order for the molecular shape to be bent
How would you describe tetrahedral?
A central atom with 4 things attached
CH4 is an example of _____
Tetrahedral for both electron pair geometry and molecular shape
Why is the electron pair geometry of SO2 trigonal planar but the electron pair geometry for H2S is tetrahedral?
SO2 is trigonal planar because it has a bond on both the oxygens and it has one set of lone pairs, making it 3 things attached to the central atom
H2S is tetrahedral because there is one bond attached to each of the Hydrogens and there are two sets of lone pairs attached to the Sulfur, making it 4 things attached to the central atom
What arrangement of elements in the lewis structure will result in the molecular shape being trigonal pyramid?
3 atoms and one lone pair on top
Ex: NH3
What are the possible molecular shapes?
Linear
Trigonal Planar
Tetrahedral
Trigonal Pyramid
Bent
What are the possible electron pair geometry?
linear
trigonal planar
tetrahedral
