3. Bonding and Chemical Interactions Flashcards
What are the two types of chemical bonds?
- Ionic bond (strongest)
- Covalent Bond
What is the octet rule?
Atoms will bond to try to create a stable octet with 8 valence electrons.
What are the elements that defy the octet rule, creating an incomplete octet with with fewer than 8 electrons?
H- Hydrogen
He- Helium (2 electrons)
Li-Lithium (2 electrons)
Be- Beryllium (4 electrons)
B- Boron (6 electrons)
What are the elements that defy the octet rule, creating an expanded number of electrons?
All elements in period three, which can extend their shell to include d orbitals.
Essentially, transitional metals
What are elements that also defy the octet rule because of the number of electrons?
Those with an odd number of electrons.
For example, NO (nitric oxide) has 11 valence electrons
How are ionic bonds and covalent bonds different?
Ionic: From between ions and involve the gain or loss of electrons
Covalent: occur when electrons are shared between atoms
Which periodic trend determines whether a covalent bond is polar or non-polar?
The polarity in a covalent bond is determined by differences in electronegativity between the two atoms.
How do you define an ionic bond?
formed via the transfer of one or more electrons from an element with a relatively low ionization energy to an element with a relatively high electron affinity
There is electron transfer, NOT sharing
What is the difference in electronegativity between two elements that result in an ionic bond?
Ionic bonds occur between elements with large differences in electronegativity (∆EN>1.7), usually between metals and nonmetals.
What are crystalline lattices? What type of bond (covalent or ionic) forms them and why?
They are large, organized arrays of ions formed by ionic compounds
Why? The attractive forces between oppositely charged ions are maximized, and the repulsive forces between the ions of like charge are minimized.
What are unique properties of ionic bonds?
- Ionic compounds tend to dissociate in water and other polar solvents
- Ionic solids tend to have high melting points
- Good conductors of heat and electricity
- Create crystal lattice arrangements to minimize repulsive forces
- Large electronegative differences
How do you define a covalent bond?
They form via the sharing of electrons between two elements of similar electronegativities
Why create a covalent bond rather than an ionic bond?
When two atoms of similar tendency to attract electrons form a compound, it is energetically unfavorable to create ions, so they share.
What does the bond order refer to?
Refers to whether a covalent bond is a single bond, double bond, or triple bond?
What are the trends as covalent bonds create more bonds (i.e. single, then double, than triple)?
As you create more bonds:
1. The bond length decreases, they get closer
2. They strengthen the bond, i.e. it takes more energy to break the bond
What is polarity and in what type of bond does it occur?
It occurs in covalent bond.
It occurs when two atoms have enough electronegative difference to draw electrons closer to one element as opposed to another, but not enough to create an ionic bond.
What’s the difference in electronegativities that polar covalent bonds occur?
∆EN= .5-1.7
When will covalent bonds be non-polar?
What are some examples?
They will occur when the ∆EN<0.5, or when the elements have the exact same electronegativity. A lot of these occur in group 7…
H2, N2, O2, F2, Cl2, Br2, I2
What is a dipole?
This is created in polar covalent bonds when one atom gets more of the shared electron than the other.
What is the equation for dipole moment and what does it mean?
p=qd
p=dipole moment
q= magnitude of the charge
d= displacement vector separating the two particle charges.
Measured in Debye Units (coulomb-meters)
It is a vector quantity of a dipole
What are coordinate covalent bonds?
They result when a single atom provides both bonding electrons, while the other atom does not contribute any.
This commonly occurs in equations where on atom is connected to H+ (i.e. the H+ atom has NO electrons, so the other atom has to give both electrons to them)
These are also called nucleophile-electrophile reactions.
What are the steps to draw a Lewis structure?
- Draw out the backbone of the structure, the least electronegative element is the middle element. The Halogens (F, Cl, Br, and I) always occupy a terminal position
- Count the number of valence electrons and add them together.
- Draw a single bond between the central atom and the atoms surrounding it (each bond counts as 2 electrons).
- Complete the octets of all atoms bonded to the central atom (except the central atom), using the remaining valence electrons
- Put the remaining atoms on the central atoms. If there are no valence electrons left, form bonds with the other atoms paired electrons (coordinate covalent bonds)
What is a formal charge, and what is the equation?
This is done to determine if a Lewis Structure is representative of the actual arrangement of atoms in a compound. They exist when an atom is surrounded by more or fewer valence electrons that it has in its neutral state (assuming equal sharing of electrons in a bond
The charge of the ion or compound is equal to the sum of the formal charges of the individual atoms comprising the ion or compound.
What is the formal charge equation, and what’s the cheat way?
Formal Charge= number of valence electrons given by column- dots - sticks
*** The charge of the ion or compound is equal to the sum of the formal charges of the individual atoms comprising the ion or compound.