Studied by 2 people
Ionic bond
A bond that occurs when valence electrons of a metal are transferred to the atom of a nonmetal
Covalent bond
A bond that occurs when 2 nonmetal atoms share electrons to attain a noble gas arrangement
What is the net charge of an ionic bond?
zero
What are the charges like in an ionic bond?
One side is more negative, and the other is more positive
How many valence electrons do most elements want?
8 - octet
How many valence electrons do Hydrogen and Helium want?
2 - duet
Ion
The number of protons does not equal the number of electrons
Cation
Positive ion
Anion
Negative ion
What ion of Magnesium would give it 8 valence electrons? What type of ion is this?
Mg → 1s²2s²2p⁶3s² - 2 electrons
1s²2s²2p⁶ = [Ne] = stable Mg²⁺ = cation
What ion of Chlorine would give it 8 valence electrons? What type of ion is this?
Cl → 1s²2s²2p⁶3s²3p⁵ + 1 electron
1s²2s²2p⁶3s²3p⁶ = [Ar] = stable Cl⁻ = anion
Do metals want to loose or gain electrons?
Loose
Do nonmetals want to loose or gain electrons?
Gain
What count of electrons do anions and cations form to?
Anions → 8 electrons
Cations → 0 electrons
How do you name cations and anions?
Cations → same name that’s on the periodic table
Anions → use the first syllable, and add “ide“ to the end
How do you draw Lewis structures for ions, polyatomic ions?
You subtract the necessary electrons, make octets, put brackets around it, and write the charge
How do you draw an atomic symbol?
Use the element symbol
Top left = mass # (protons + neutrons)
Bottom left = atomic number (protons)
Top right = charge (if no charge, don’t write anything)
When calcium looses two electrons what would you call it?
When chlorine gains an electrons, what would you call it?
Calcium
Chloride
Ionic Compound
Consist of positive and negative charges (ions) held together by the strong electrical attraction between oppositely charged ions
Specifics of ionic compounds
Have ionic bonds
High melting points
Solids at room temperature
Chemical Formula
No charges in the formula
The symbols and subscripts are written in the lowest whole # ratio of the atoms or ions
Net charge should be 0
Total positive charge = Total negative charge
Naming ionic compounds
Metal and then nonmetal =
cations and anion meaning the second word will end with an “ide“
No capitals
What is the difference between superscript number and subscript number in an ionic compound?
Superscript = charges
Subscript = # of atoms
What are the charges for these groups?
1
2
3
15
16
17
18
1 = 1+ cation
2 = 2+ cation
3 = 3+ cation
15 = 3- anion
16 = 2- anion
17 = 1- anion
18 = 0
What are the net charges of…
Aluminum
Zinc
Cadmium
Silver
These, we must have memorized
Aluminum = 3+ cation
Zinc = 2+ cation
Cadmium = 2+ cation
Silver = 2+ cation
For any transition metal, or any element that we have not memorized the charge for, what do you do?
We use a roman numeral; by looking at what its bonded to
What is the name of FeCl₂?
Fe = iron; we don’t know the charge
Cl₂ = 2 chlorine and we know that chlorine has a charge of 1- and since there are two of them, the overall is -2 and we would call it chloride
Now, we need to balance out the ion with the iron. We can do this by creating a +2, so we will choose iron II.
iron(II) chloride
What are the formulas?
nickel (II) sulfide
zinc chloride
nickel (II) sulfide
Nickel, we are given the two, so we know the charge is 2+ now we just have to figure out the sulfide. Sulfur’s charge is 2-, as we can tell using the periodic table, and we need 2- to combat the 2+, which works perfectly here NiS
zinc chloride
Zinc is one the elements we memorized, so we know it has a 2+ charge. Chlorine has a charge of -1, as shown on the periodic table, and since we need a 2- to combat the 2+ we add another atom of chlorine! ZnCl₂
Polyatomic Ions
Group of covalently bonded atoms w/ an ionic charge
What types of charges do polyatomic ions usually have?
1-, 2-, 3-
Negatives
What types of atoms are usually in polyatomic ions?
Nonmetals such as P, S, C, N, O
Which polyatomic ions are the only positive ones?
Hydronium (H₃O⁺) and Ammonium (NH₄⁺)
What do polyatomic ions end in? What are the exceptions?
-ate or -ite
OH⁻ and CN⁻ (Hydroxide and Cyanide)
How would you combine a magnesium ion and and a nitrate ion?
Magnesium = 2+ (from periodic table)
Nitrate = polyatomic ion NO₃⁻ aka 1-
So, just like we would do with any ionic compound, we need to balance out the charges. Here, we can do this by adding a nitrate ion.
Now, we need to add a subscript 2 to represent the amount of nitrate atoms, BUT since there is already a subscript, we put parenthesis around the NO₃.
Remember, no charges! Mg(NO₃)₂
Name FePO₄
Fe = Iron and we don’t know the charge
PO₄ is a polyatomic ion!, we have these memorized, so we know its phosphate and the charge is 3- meaning we need a 3+ to combat it! So we simply use that charge for the iron giving us Iron(III) Phosphate
Molecular Compounds
Have covalent bonds
No charge
Between 2 nonmetals
Valence electrons shared by nonmetal atoms to achieve stability
Molecule
A discrete group of atoms in a definite proportion
H₂O = always in that proportion and doesn’t go on, merge with other H₂O to make a larger H₂O
Naming Covalent or Molecular Compounds
Like ionic compounds, the first word stays the same as on the periodic table
Second work, needs an “ide“
Difference:
PREFIXES
If there is only one of the first atom, then keep the name, but if there are any more, use the proper prefix that corresponds to the number.
For the second word, even if there is one, use the proper prefix, one being mono-
Prefixes (1-10)
1 = mono-
2 = di-
3 = tri-
4 = tetra-
5 = penta-
6 = hexa-
7 = hepta-
8 = octa-
9 = nona-
10 = deca-
What is the rule with o and a when naming molecular compounds?
If there is either oo, ao, oa, aa, then you drop the first vowel.
Name these:
N₂O
Cl₂O₇
CO₂
N₂O = dinitrogen monoxide
Cl₂O₇ = dichloride heptoxide
CO₂ = carbon dioxide
What is diphosphorus pentoxide’s formula?
P₂O₅
Which polyatomic ion can form an ionic bond with other nonmetals and why?
NH₄⁺ (Ammonium) because the entire charge is positive, creating ionic bonds with negatively charged nonmetals
What are the types of pairs in Lewis Structures
Double bonds
Bonding pairs
Nonbonding pairs/lone pairs
How are the two types of bonds portrayed in Lewis Structures?
Bonding pairs = lines
Lone pairs = two dots side-by-side
Electronegativity
An atom’s ability to attract the shared electrons in a chemical bond
What is the trend of electronegativity on the periodic table?
Left to right = increases
Top top to bottom = decreases
When drawing Lewis Structures, what must you always form?
Octets!
Hydrogen and Helium = duets
Diatomic Molecules
Double bonded pairs of atoms
H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂
What type of molecule are diatomic molecules?
Covalent, Nonpolar
Formulas for methane, ammonia, and water
Methane = CH₄
Ammonia = NH₃
Water = H₂O
What is a central atom?
The atom to which the other atoms are attached to
The one in the center
How do you calculate the number of valence electrons when making Lewis Structures?
Number of valence electrons x number of atoms of that element
Do for each element and add up the values
Double Bonds
When atoms share two pairs of electrons
Triple Bonds
When atoms share three pairs of electrons
Why do double and triple bonds form?
When there aren’t enough electrons to create octets
What do halogens like to have, and where in a molecule do they like to be?
3 lone pairs, terminal = on the ends
What does carbon like to do in molecules?
Like to bond to itself, wants to be in the center, have 4 bonds somehow
What can hydrogen not have in a molecule, and where can’t it be?
Can’t handle more that 2 electrons, cannot be in the middle
If you have a cation, what did you do with electrons
subtract electrons
If you have an anion, what did you do with electrons
add electrons
What are the electronegativity ranges?
TOTAL = 0.0 - 4.0
Non-polar Covalent = 0.0 - 0.4
Polar Covalent = 0.5 - 1.8
Ionic = 1.9 - 4.0
Electronegativity: Which element is the most attractive and which is the most generous?
Attractive = Fluorine
Generous = Cesium
Is electronegativity higher for metals or nonmetals?
Nonmetals
How can you determine the polarity of a compound?
Use general
Uneven/unsymmetrical = polar
Even/symmetrical = nonpoalr
Find the dipole
Difference in electronegativity
Dipole
Separation of charges in a charged molecule (usually polar)
A bond or molecule whose ends have opposite charges
What happens as the electronegativity increases in a polar bond?
The bond becomes more polar
What does VSEPR Theory stand for?
Valence Shell Electron-Pair Repulsion Theory
What does the VSEPR Theory state?
Electron groups are arranged as far apart as possible around the central atom
What does the VSEPR Theory show/describe?
Shape
Linear: types of pairs and angle degree
Pairs: 2 bonded atoms, 0 lone pairs
Angle: 180°
Trigonal Planar: types of pairs and angle degree
Pairs: 3 bonded atoms, 0 lone pairs
Angle: 120°
Bent (Trigonal): types of pairs and angle degree
Pairs: 2 bonded atoms, 1 lone pairs
Angle: <120°
Tetrahedral: types of pairs and angle degree
Pairs: 4 bonded atoms, 0 lone pairs
Angle: 109°
Trigonal Pyramidal: types of pairs and angle degree
Pairs: 3 bonded atoms, 1 lone pairs
Angle: <109°
Bent (Tetrahedral): types of pairs and angle degree
Pairs: 2 bonded atoms, 2 lone pairs
Angle: <<109°
Can nonpolar molecules have polar bonds?
Yes, as long as their dipoles cancel out
What happens if dipoles point to the same molecule?
They do not cancel out and instead add up
Reinforce eachother
Intermolecular Forces
Forces between two atoms/molecules
Are intermolecular forces covalent or ionic?
Covalent
What are the three types of intermolecular forces?
Dipole-Dipole Attractions, Hydrogen Bonds, Dispersion Forces
Dipole-Dipole Attractions
Polar molecules
Hydrogen bonds are part of this; don’t always occur
Hydrogen Bonds
Polar molecules
First, we check for Dipole-Dipole
If H is bonded to F, N, or O, then it is a Hydrogen bond
Dispersion Forces
Non-polar Molecules
Only type of non-polar bond
Enables non-polar molecules to form solids and liquids
Which intermolecular force is weakest, which is the strongest?
Weakest = dispersion forces
Strongest = hydrogen bond
Are ion bonds/ ion dipoles stronger than intermolecular forces?
Yes, they are extremely strong
How do intermolecular forces correspond with melting points?
The stronger the force, the more energy it will take to break those bonds, and vice-versa
Non-polar molecules have a lower melting point than polar molecules due to their intermolecular forces
Between NH₃ and PH₃, which has the higher melting point?
Both of them are polar molecules, however, NH₃ has a hydrogen bond while PH₃ only has dipole-dipole
Therefore, NH₃ has the higher melting point
Note 
Flashcard (30)