Honors - Unit 3 - Ionic/Covalent Flashcards
Bond Pairs
Pairs of electrons which form a bond.
Lone Pairs
Electron pairs which are not involved in bonding. They do however, affect the shape because electron pairs repel other electron pairs.
Rules for Writing Lewis Dot Structures
- Total the Valence Electrons and Update during each step.
- Form a single bond between the central atom and each surrounding atom (each bond uses two electrons).
- Place electrons around the outer atoms until you run out or they each have eight electrons around them. (Hydrogen and Helium can only have two electrons around them).
- Place any remaining electrons around the central atom.
- Does each atom other than hydrogen have eight electrons around it?
- Rearrange (share) electrons so that all atoms other than hydrogen have eight electrons around them.
Octet Rule
All atoms other than hydrogen and helium bond to fill their valence shell with eight electrons.
Duet Rule
Hydrogen bonds to fill it’s valence shell with two electrons. Helium already has two electrons and thus does not need to form bonds to increase stability.
Violations of the Octet Rule
Be - 4
B - 6
P - 8 or 10
S - 8, 10, or 12
Xe - 8, 10, or 12
VSPER
Valence Shell Electron Pair Repulsion
Most important aspect of determining the shape or geometry of a molecule. The molecule will adopt the shape which minimizes te electron pair repulsion.
What is the Lewis dot structure of Br₂?
What is the Lewis dot structure of XeF₄?
What is the Lewis dot structure of [NO₂]‾¹?
What would the Lewis dot structure of OC be?
Hydrogen
Group 1 Nonmetal
Ionic Bond
Metals GIVE electrons, Nonmetals TAKE electrons
Naming Ionic Bonds
State the name of the metal followed by the nonmetal with the ending changed to “ide”. If the metal is a transition metal, add a (Roman numeral). AlCl₃ = Aluminum Chloride CuCl₃ = Copper (III) Chloride
Writing Formulas for Ionic Bonds
Absolute Value Criss Cross Oxidation #’s
Polyatomic Ion
A group of atoms that acts like an ion (has a charge)
Properties of Ionic Compounds
Crystalline Structure High Melting Point Rigid Strong Bond Conduct Electricity (when dissolved or melted) Good Insulators
Covalent/Molecular Bonding
Nonmetals SHARE electrons
Intermolecular Forces
Attractive forces BETWEEN molecules.
Van Der Waals or London Dispersion Forces are the weakest type of intermolecular force and hydrogen bonds are the strongest.
Intramolecular Forces
Attractive forces WITHIN a molecule (Ionic & Covalent Bonds)
These bonds are stronger than intermolecular forces.
Polar Covalent
A type of covalent bond between two atoms in which electrons are shared unequally. Because of this, one end of the molecule has a slightly negative charge and the other a slightly positive charge.
Non Polar Covalent
A type of covalent bond between two atoms in which electrons are shared equally.
Naming Covalent Compunds
You DO NOT use the “criss-cross” method. Use prefixes. The only time you do not use a prefix is when there is only one of the first nonmetal. Remember : 1-Mono 2-Di etc…
Write the formula for Mg²⁺ and PO₄³⁻
Using the criss-cross method and subscripts to insure sum of charges is zero: Mg₃(PO₄)₂
Polyatomic Ionic Formulas
- Metal written first, Polyatomic Ion is written second 2. Use criss-cross method and subscripts to insure sum of charges = 0 3. When using a subscript for polyatomic ions: place a parentheses around the polyatomic formula, put the subscript outside of the parentheses
Polyatomic Ion
Polyatomic Ions ions made up of more than one atom; acts as an individual ion in a compound; charge applies to entire group of atoms.
Ionic Compounds
two words, first names cation second names anion. Indicate charge of transition metal cation by Roman Numeral. MgCl₂ = Magnesium Chloride Cr(NO₃)₃ = Chromium(III) Nitrate SnCl₂ = Tin(II) Chloride
Anions
Anions are named by adding the suffix -ide to the stem of the name of the nonmetal from which they are derived. N³⁻ = Nitride O²⁻ = Oxide F⁻ = Flouride
Ionic Compound Formulas
- Metal written first Nonmetal written second 2. Use criss-cross method and subscripts to insure sum of charges = 0
Oxidation Number
Ion Charge - number of electrons transferred to or away from an atom when it becomes an ion.
Greek Prefixes used in nomenclature 1= 2 = 3 = 4= 5 = 6= 7= 8= 9= 10=
1= mono 2 =di 3 =tri 4=tetra 5 = penta 6=hexa 7=hepta 8=octa 9=nona 10=deca
Covalent or Molecular Compounds (Molecules)
The first word gives name of the element that appears first preceded by a prefix that shows number of atoms in that element. Do NOT use the prefix mono before the name of the first element. The second word consists of a prefix designating the number of atoms of that element, the stem name of the second element, and the suffix -ide.
(Oxidation #) Charge of Group17 or 7A (F, Cl, Br, I)
Charge: 1-
(Oxidation #) Charge of Group 16 or 6A (O,S, Se, Te):
Charge: 2-
Charge of Group15 or 5A (N, P, As):
Charge = 3-
(Oxidation #) Charge of Group 2 or 2A (Be, Mg, Ca, Sr, Ba):
Charge = 2+
(Oxidation #) Charge of Group 1 or 1A (H, Li, Na, K, Rb, Cs):
Charge = 1+
Ionic Compounds
Conduct Electricity when melted or dissolved in water because….
Cation Formation
Metals give electrons to become like the nearest noble gas.
Anion Formation
Nonmetals recieve electrons when forming an ionic compound so that their electron configuration will be like the nearest noble gas.
Compound Formation
Compounds are the result of the formation of chemical bonds between two or more different elements, whose atoms lose, gain or share valence electrons to complete their outer shell and attain a noble gas configuration.
This tendency of atoms to have eight electrons in their outer shell is known as the octet rule.
Summarize the rules for naming ionic and covalent compounds.
Summarize how to write formulas for ionics and covalents.
