Chemical Bonding
Why are the valence electrons of an atom the only electrons likely to be involved in bonding to other atoms?
E- in full energy levels (core e-) do not need to gain or lose e- to have full orbitals. Only valence orbitals need to gain or lose e- to achieve a noble gas configuration.
On the basis of the electronegativity values, indicate whether each of the following bonds would be ionic, covalent, or polar covalent? H - F
ionic
On the basis of the electronegativity values, indicate whether each of the following bonds would be ionic, covalent, or polar covalent? Na - Br
ionic
On the basis of the electronegativity values, indicate whether each of the following bonds would be ionic, covalent, or polar covalent? Cl - Cl
nonpolar covalent
On the basis of the electronegativity values, indicate whether each of the following bonds would be ionic, covalent, or polar covalent? As - Se
polar covalent
On the basis of the electronegativity values, indicate whether each of the following bonds would be ionic, covalent, or polar covalent? H - O
polar covalent
How many electrons are involved when two atoms in a molecule are connected by a "double bond"?
4 e-
What does it mean to say that a bond is polar?
A bond is polar when the shared e- are closer to one of the bonded atoms (due to that atom having a larger electronegativity value).
What is a chemical bond?
A force that hold groups of 2 or more atoms together
What is a dipole moment?
A molecule has a dipole moment if it has an area of partial positive charge and an area of partial negative charge.
Although both the BF₃ and the NF₃ molecules contain the same number of atoms, the BF₃ molecule is flat whereas the NF₃ molecule is trigonal pyramidal. Explain.
BF₃ has 3 e- areas (3 bonded and zero lone pairs) so the milecule is flat - trigonal planar. NF₃ has 4 areas of e- (3 bonded and one lone pair)- the lone pair of e- given the molecule a tetrahedral electronic shape and also makes the molecular shape be 3-D (pyramid)
Predict the formula of the simple binary ionic compound likely to form when the pairs of elements react with each other. barium, Ba, and selenium, Se
BaSe
On the basis of the electronegativity values, indicate which bond of the following pairs is more polar. Cl - S or Se-Br
Cl - S
What type of bonding involves the sharing (either equally or unequally) of electrons between atoms?
Covalent
Explain the difference between a covalent bond formed between two atoms of the same element and a covalent bond formed between atoms of two different elements.
Covalent bond with atoms of same element: e- in the bond are most likely shared equally between the 2 atoms. Covalent bond with atoms of different elements: e- in the bond are most likely shared unequally between the 2 atoms (depends on the electronegativity of the atoms).
Explain how the atoms in covalent molecules achieve configurations similar to those of noble gases. How does this differ from the situation in ionic compounds?
Covalent molecules: atoms (nonmetals) share e- to fill valence orbitals (s&p) Ionic compounds: metals transfer e- to nonmetals, so each will have full valence orbitals.
What do chemists mean by the therm electronegativity?
Electronegitivity is the relative ability of an atom in a molecule to attract shared e- to itself.
Does the fact that a molecule posses polar bonds mean that the molecule itself will also be polar?
If the dipole moments of each bond cancel out (due to strength and shape of the molecule) then the molecule is nonpolar.
What type of bonding requires the complete transfer of an electron from one atom to another?
Ionic
On the basis of the elctonegativity values, indicate which bond of the following pairs is more polar. N - Cl or K - Cl
K - Cl
Predict the formula of the simple binary ionic compound likely to form when the pairs of elements react with each other. potassium, K, and hydrogen, H
KH
Predict the formula of the simple binary ionic compound likely to form when the pairs of elements react with each other. lithium, Li, and nitrogen, N
Li₃N
What type of atoms usually make an Ionic bond?
Metals with Nonmetals
Predict the formula of the simple binary ionic compound likely to form when the pairs of elements react with each other. magnesium, Mg, and bromine, Br
MgBr₂
On the basis of the electroonegativity values, indicate which bond of the following pairs is more polar. Na - O or N - O
Na - O
Predict the formula of the simple binary ionic compound likely to form when the pairs of elements react with each other. sodium, Na, and sulfur, S
Na₂S
What type of atoms usually make a Covalent bond?
Nonmetals only
Describe the type of chemical bonding that exists between the atoms in the H₂ molecule.
Nonpolar covalent
Describe the type of chemical bonding that exists between the atoms in the HF molecule.
Polar covalent
What is the geometric structure of the water molecule? How many pairs of valence electrons are there on the oxygen atom in the water molecule? What is the approximate H-O-H bond angle in water.
Tetrahedral, bent, 2 lone pairs and 2 bonded pairs of e-, 109°
What is the geometric structure of the ammonia molecule How many pairs of electrons surround the nitrogen atom in NH₃? What is the approximate H-N-H bond angle in ammonia?
Tetrahedral, trigonal pyramid, 1 lone pair & 3 bonded pairs of e-, 109°
What are the conditions that give rise to a bond's being polar?
The greater the electronegativity difference, the more polar the bond.
What does its electronegativity tell us about an atom?
The larger the electronegativity value, the closer the shared e- tend to be to that atom when it forms a bond.
Explain how the valence shell electron pair repulsion theory (VSEPR) is used to predict the arrangement of the electron pairs about the central atom.
The structure around a given atom is determined by minimizing repulsion between e- pairs.
On the basis of the electronegativity values, indicate which bond of the following pairs is more polar. N - C or B - C
They are equal
What is the geometric structure of the boron triflouride molecule, BF₃? How many pairs of valence electrons are present on the boron atom in BF₃? What are the approximate F-B-F bond angles in BF₃?
Trigonal planar, trigonal planar, 0 lone pairs and 3 bonded pairs of e-, 120°
Draw a figure indicating the direction of the bond dipole, including which end of the bond is positive and which is negative. Cl - F
→ Cl - F
Draw a figure indicating the direction of the bond dipole, including which end of the bond is positive and which is negative. H - F
→ H - F
Draw a figure indicating the direction of the bond dipole, including which end of the bond is positive and which is negative. I - Cl
→ I - Cl