Unit #2: Lesson 2.2
Describe how a covalent bonds.
A covalent bond occurs when the attraction between the nuclei is the greatest for the shared electrons, but the repulsion between electrons and between the nuclei is the least. If the atoms are too close together the nuclei will repel each other and if they are too far apart the attraction will not be enough to hold them together.
Describe repulsion and attraction during chemical bonds.
Balance between attraction (protons and electrons) and repulsion (proton-proton and electron-electron).
Interactions between cations and anions can be explained with ______________ law.
Coulomb's F = k (q1 q2} / r2
Ionic Bonds
Electrostatic attraction between a cation (positively charged ion) and anion (negatively charged ion).
____________________ the bond order increases the bond energy, as there are more electrons involved and therefore ____________________ Coulombic attraction and the bond length has decreased.
Increasing greater
Larger ion charge = ________________ force of attraction
Larger
Describe a triple bond.
Most shared electrons The stronger attraction between the nucleus of one atom and the bonding electrons Stronger and shorter bond Strength: Strongest Length: Shortest
Greater distance between charges = _________________ force of attraction.
Smaller
Describe a double bond.
Strength: Middle Length: Middle
The energy required to separate the ions in the Mg(OH)2 crystal lattice into individual Mg+2 (g) and OH-1 (g) ions, as represented below, is known as the lattice energy of Mg(OH)2 (s). As shown below, the lattice energy of Sr(OH)2 is less than the lattice energy of Mg(OH)2 (s). Explain why in terms of periodic properties and Coulomb's law. Reaction: Mg(OH)2 (s) ----> Mg+2 (g) + 2 OH-1 (g) Lattice Energy (KJ/mol): 2900 KJ/mol Reaction: Sr(OH)2 (s) ----> Sr+2 (g) + 2 OH-1 (g) Lattice Energy (KJ/mol): 2300 KJ/mol
The Sr+2 ion is larger than the Mg+2 ion because it has more occupied energy shells. Coulomb's law states that the force of attraction between the cation and anions is inversely proportional to the square of the distance between them. Since the distance between Sr+2 and OH-1 is longer than the distance between Mg+2 and OH-1, the attractive forces in Sr(OH)2 are weaker and its lattice energy is also smaller. Overall, it takes less energy to separate the elements (in the ionic solid)
Chemical Bond
The attraction between the nucleus of one atom and the electrons of another atom.
Describe a single bond.
The fewest electrons are shared The weaker attraction between the nucleus of one atom and the bonding electrons Weaker and longer bond Strength: Weakest Length: Longest
The potential energy diagram is given for C-O (triple bond). A student claims that the curve for C-O (single bond) would be less deep and it would be shifted to the right of the curve for C-O (triple bond). Do you agree with this claim? Explain why or why not.
Yes, I agree. In the C-O (single bond) bond, there are less electrons being shared (2 v.s. 6), so the nucleus of carbon (or oxygen) will be less attracted to the bonding electrons. As a result, the bond length will be longer, and the bond energy will be less than the C-O (triple bond).
If there are not attractive or repulsive forces between the atoms the potential energy is _____________.
Zero
Larger charges = more ___________________ = ________________ energy required to separate ions.
attraction more
Smaller radii = more _______________________ = _____________ energy required to separate ions.
attraction more
Longer bond length ________________ the bond energy.
decreases
Bond breaking is an....
endothermic process
Larger atomic radius ___________________ bond length.
increases
Bond order
is defined as the difference between the number of bonds and anti-bonds.
Bond length
is the distance between atoms.
Bond energy
is the energy required to break a chemical bond.
Lattice energy
is the energy used to separate ions in ionic compounds is their lattice energy. It is defined as the change in energy that takes place when gaseous ions are combined to form an ionic solid. Combining ions will release energy. energy expelled (negative) / Ions ------> ionic solid
Equation for lattice energy:
k(Q1Q2) / r
Bond energy can be determined by...
looking at the lowest point of the line on the graph.
Covalent bonds occur at the ______________ energy state.
lowest
A stable chemical bonds is when the potential energy (KJ/mol) is __________________.
negative
Covalent bonds are the bonds between two ________________ when they share _________________________________________________.
nonmetals valence electrons
The internuclear distance (pm) is located...
on the x-axis of the graph.
The PE is located...
on the y-axis of the graph.
Covalent bonds can be ______________ or ____________________, meaning that the electrons are shared unequally or equally.
polar nonpolar
An unstable chemical bonds is when the potential energy (KJ/mol) is __________________.
positive
Bond energy is _____________.
positive
Covalent bonds can be _________________, _______________________, and ___________________ bonds or an average of those if there are resonance structures.
single double triple
Coulomb's Law
the attraction between charged particles increase as the distance between them decreases.
The reason why the energy on the graph (y-axis) is negative is because...
the diagram or graph is about formation, not about bond breaking, so the bond energy would be the same value just opposite sign (it would be positive)
Bond energy is...
the energy required when breaking a bond, or the energy released when a bond is formed. The magnitude is the same, but the sign is different.