Answer all Problems: Distinguish among ionic, covalent, and metallic bonding. Wh

Question

Answer all Problems:

Distinguish among ionic, covalent, and metallic bonding. Which of the following molecules possess polar covalent bonds: H2, N2, HC1, HCN, and CO2? Which of the molecules in question 2 have molecular dipole moments? What are the favored geometrical arrangements for ABn molecules for winch the A atom has 2, 3,4, 5, and 6 pairs of electrons in its valence shell? How many equivalent orbitals are involved in each of the following sets of hybrid orbitals: sp, sp2, sp 3d, and sp3d2? Define the term formal charge. Calculate the formal charges of the atoms in CO, CO2 , and CO32 - .

Explanation / Answer

In ionic bonding, positive and negative ions become attracted to each other and form a solid lattice structure in which cations (positive ions) surround themselves with anions (negative ions) and anions surround themselves with cations. These ions come about from reactions in which one species loses electrons to gain a noble gas electron configuration, while another species takes in the electrons also to attain a noble gas valence shell of eight electrons.

In covalent bonding, no species actually lose or gain electrons. Rather, electrons are shared among the species in the bond. The attraction of each species to the electrons creates the bond.

In metallic bonding, a series of metal atoms of one element combine together and allow electrons to flow freely among them (the key word is delocalized electrons). The nuclei of the metal atoms are attracted to the delocalized electrons, causing the bonding to form.

2. H2 and N2 are both nonpolar covalent bonds. They contain only one species and have linear geometry. Each atom pulls equally hard on the electrons, so no polarity occurs. CO2 is also nonpolar covalent because it is linear with oxygens pulling on the electrons around the carbon equally in opposite directions. The opposite pulls cancel.

HCl is polar covalent because the electronegativity difference between H and Cl is very large, causing electrons to be more attracted to Cl, the species with the higher electronegativity. HCN is also polar covalent. The electrons in the H-C bond favor C because of its higher electronegativity, and the electrons in the C-N bond slightly favor N for the same reason. The H end of the molecule thus tends to be more positive than the N end.

3. HCl and HCN both have molecular dipoles. The dipole in HCl has the positive end facing H and the negative end facing Cl. For HCN, the positive end faces H and the negative need faces N. CO2 does not as the two dipole moments cancel each other out.

5. 4. The sp hybrid results from an s and p orbital, and so it has two orbitals. sp2 involves an s and two p atomic orbitals, so 3 molecular orbitals result. sp3 involves an s and three p atomic orbitals, so four molecular orbitals result. By the same logic, sp3d has 5 molecular orbitals and sp3d2 has 6. A key rule of thumb is that there is a conservation of orbitals when atomic orbitals merge to form bonding orbitals. For example, if two atomic orbitals are lost, two bonding orbitals must result.

6. Formal charge is a way of determining the stability of a lewis structure. It is used to decide which is the best structure when multiple possibilities arise. It is calculated by taking the initial number of valence electrons on the central atom and subtracting the number of lone pair electrons and subtracting 1/2 times the number of shared electrons pairs (those involved in bonding with other atoms).

7. Formal Charge = Valence electrons - (number of bonds + number of spare electrons on the atom)

In the Lewis structure of CO, There are are 3 bonds between them and 2 electrons (one lone pair) on each atom.

Formal Charge of Oxygen in CO= 6 - (3 + 2) = 1

Formal Charge of Carbon in CO= 4 - (3 + 2) = -1

It is neutral because both of the formal charges (-1 and 1) add up to 0

formal change of the atom in CO2

formal change of left O = +1

formal change of carbon = 0

formal change of the right O = -1

sum up the formal change = 0

[CO3]2-

Carbon F.C = 0

Oxygen F.C = -1

Oxygen F.C = -1

Oxygen (double bond) F.C = 0

NET CHARGE --> -2...

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