Ionic Bonds
What holds atoms together in an ionic bond?
The positive and negatively charged ions.
What holds atoms together in covalent bonds?
The shared electrons form single, double or triple bonds that hold the atoms together. The electrons are attracted to the positively charged nucleus of each atom.
What holds atoms together in metallic bonds?
The metal atoms give up their valence electrons into the electron sea, which is negatively charged. All those negatively charged electrons are attracted to the positively charged nucleus, which holds the atoms together.
What does VSEPR stand for?
Valence Shell Electron Pair Repulsion
An unknown substance is an excellent electrical conductor in the solid state and is malleable. What type of chemical bonding does this substance exhibit?
Metallic bond
Describe the general shape of an ionic compound and how the bond type drives the shape?
Crystalline structure.
Each positive ion attracts negative ions, creating the lattice structure.
(this makes the compound hard and brittle)
For the following examples, which has the greater bond energy:
a. Single bond or Double bond
b. A bond length of 92pm or bond length of 199 pm
a. Double bond (the more bonds, the greater the energy, the stronger they are)
b. 92 pm bond length (the shorter the bond length, the stronger the bond, the greater the bond energy)
Describe the sea of electrons:
- where do the electrons come from?
- how do they explain a metal's ability to be ductile and malleable?
- The electrons are from the valence electrons from the metallic atoms.
- since the electrons flow freely, the atoms are able to move freely as well - constantly balancing charges - so the metal can be hammered into sheets and pulled into a wire
According to VSEPR what molecular geometry would the following molecules take on?
AB3E
AB2E2
AB2E
AB3E - trigonal-pyramidal
AB2E2 - bent
AB2E - bent
Why are metals good conductors of electricity?
The ability of electrons to move freely about thee structure.
Compare/contrast polar covalent bond and an ionic bond.
(need at least 1 similarity and 1 difference)
Similarity:
- unequal "sharing" of electrons
- compound has neutral charge
- each atom has some type of a charge
- difference in charge holds compound together
Differences:
- complete giving away of electrons vs. unequal sharing of electrons
- ions vs. "slightly charged" atoms
- physical and chemical properties will be different
Which molecule contains a double bond?
A. COCl2
B. C2H6
C. CF4
D. SF2
COCl2
For covalent bonds, double bonds are shorter/longer and stronger/weaker than single bonds.
shorter
stronger
List the intermolecular forces.
Dipole-Dipole
Hydrogen Bond
London Dispersion Forces
Explain why ionic crystals are brittle.
Ionic crystals are brittle because shifting of the layers of ions results in large repulsive forces that cause the layers to part completely.
Write the ionic formula unit for the following compounds:
Ca and P
K and S
Ba and O
Ca3P2
K2S
BaO
Draw the lewis structure for HCN. How many unpaired electrons are there?
2 unpaired electrons on N.
C is central atom.
Single bond between C and H
Triple bond between C and N
How is electronegativity used in determining bond type? Be specific, including the calculation and thresholds.
The difference in electronegativity determines bond type.
If the difference is between 0 and 0.5 the bond is nonpolar covalent.
If the difference is between 0.5 and 2.1 the bond is polar covalent.
If the difference is greater than 2.1 the bond is ionic.
On the basis of bond polarity and orientation, determine the molecular geometry and if the bond will be polar.
CF4
tetrahedral
nonpolar since everything is balanced
What types of elements create each bond type?
Metallic
Ionic
Covalent
Metallic - metals
Ionic - metal and nonmetal
Covalent - two nonmetals
In general, how do ionic and molecular compounds compare in terms of melting points, boiling points, and ease of vaporization?
Ionic compounds have higher melting points and boiling points than molecular compounds do, and they do not vaporize at room temperature.
Draw the lewis structure and determine if the following molecule is polar:
CH2O
C is the central atom.
There are 2 single bonded H atoms to C.
There is a double bonded O atom to C.
Despite the shape being able to create a balanced/nonpolar molecule, the atoms attached have different electronegativity values, so it will be a polar molecule.
What are the 3 types of energy used to measure bond "strengths" and their associated bond types?
Ionic - Lattice Energy (energy to create the bond)
Covalent - Bond Strength (Energy to break the bond)
Metallic - Enthalpy of Vaporization (energy to vaporize the metal)
On the basis of bond polarity and orientation, determine the molecular geometry and if the bond will be polar.
NH3
Trigonal Pyramidal
polar given the unpaired electron pair
What type of bond type often dissolves in water and then conducts electricity?
Ionic Bonds