Chapter 3: Bonding and Chemical Interactions Flashcards
(28 cards)
Molecules:
These are formed when atoms of most elements, except a few noble gases can combine to form molecules.
• Atoms within these molecules are held together by strong attractive forces called chemical bonds.
Octet Rule:
Exceptions to this rule:
This rule states that an atom tends to bond with other atoms so that it has 8 electrons in its outermost shell, thereby forming a stable electron configuration similar to that of noble gases.
• Exceptions to the rule:
○ Incomplete Octet, Expanded Octet, Odd Number of electrons.
Incomplete Octet:
This is an exception to the octet rule where elements are stable with fewer than 8 electrons in their valence shells and include hydrogen (2 electrons), helium (2), lithium (2), beryllium (4), and boron (6).
Expanded Octet:
This is an exception to the octet rule where any element in period 3 or greater can hold more than 8 electrons, including phosphorus (10), sulfur (12), chlorine (14), and many others.
Odd Octet:
This is an exception to the octet rule where any molecule with an odd number of valence electrons cannot distribute those electrons to give 8 to each atom.
How is Ionic Bonding formed, & where does it occur:
This bonding is formed when one or more electrons from an atom with a low ionization energy, typically a metal, are transferred to an atom with a high electron affinity, typically a nonmetal.
• Occurs between elements with large differences in electronegativity, usually between metals and nonmetals.
It includes ionic compounds.
Ionic Compounds:
In ionic bonding these compounds form crystalline lattices - large, organized arrays of ions.
They also tend to dissociate in water and other polar solvents.
How are Covalent Bonding formed?
This bonding is formed when an electron pair is shared between two atoms, typically non-metals, that have similar values of electronegativity.
Covalent Bonds include:
Bond order, degree of polarity, and coordinate bonds.
Bond Order:
This is whether the covalent bond is a single, double or triple bond.
○ As the bond order increases, the bond strength and bond energy increases, and the bond length decreases
Bond Length:
This is under bond order. This is the average distance between the two nuclei of atoms in a bond.
□ The two atoms are pulled together which decreased bond length when the # of shared electrons increase.
® Example: Triple bond would be shorter than a double bond, but triple will have the strongest bond and most energy.
Bond Energy:
This is under bond order. This is the energy that is needed to break a bond by separating its components into their isolated, gaseous atomic states.
□ More # of shared electrons.
Polarity:
This is under bond order. This is when two atoms have a relative difference in electronegativities.
□ These two come together to determine which electron pair will be shared.
® The atom with the higher electronegativity gets the larger share of electronegativity gets the large share of the electron density.
Nonpolar Covalent Bonds:
This bond is when atoms have identical or close to identical electronegativities share electron pairs.
® There is no separation of charges across the bond.
® Mostly the 7 diatomic atoms, like H2, N2, O2, F2, Cl2, Br2, and I2.
Polar Covalent Bonds:
This bond is when atoms that differ in their electronegativity will share electrons unevenly.
® Electronegativities will be around 0.5-1.7 and not enough to form ionic bonds.
® It will have dipole moment.
® It will cause a separation of charges across the bond.
◊ Partial Positive Charge + Partial Negative Charge.
Partial Negative Charge:
When covalent bonds have this. It means that the more electronegative element will have a larger portion of electron density.
Partial Positive Charge:
When covalent bonds have this. It means that the less electronegative element will have a smaller portion of electron density.
Dipole Moment:
This is the a vector quantity for polar bonds or polar molecules.
◊ Equation: p = qd
p is the dipole moment, q is the magnitude of the charge, and D is the displacement separating the two partial charge.
What determines the degree of polarity:
The degree to which the pair of electrons is shared equally or unequally between two atoms determines the degree of polarity.
○ Example: if the electrons are shared equally, the covalent bond is nonpolar, if it is unequally, then it is polar.
Coordinate Bonds:
These are bonds, when only both of the shared electrons are contributed by only one of the two atoms.
○ Basically the lone pair of one atom attacks another atom with an unhybridized p-orbital to form a bond.
○ Typically found in Lewis acid-base reactions.
Lewis Acid:
Lewis Base:
Lewis Acid: is a compound that will accept a lone pair of electrons.
Lewis Base: is a compound that will donate a lone pair of electrons.
Covalent Bond Notation:
Includes the lewis structure, and the formal charge.
Lewis Structure:
This structure is the system of notation that was made to keep track of the bonded and nonbonded electron pairs.
More than one can be drawn for a molecule.
This is the chemical symbol of an element surrounded by dots, each representing one of the s or p valence electrons of the atom.
Example: Nitrogen: It has 5 valence electrons so there will be 5 dots around the N.
Formal Charge:
This is the# of valence electrons - # of non-bonding electrons - # of bonds.
