CH 221z Exam 2 Review

Electron Configurations

100

What principle does this violate?

Pauli exclusion principle

200

What is the condensed electron configuration for the zinc ion? 

[Ar] 3d10 

The neutral atom of zinc has this electron configuration: [Ar] 4s2 3d10. Remember with transition metals, the electrons are pulled from the s subshell first, as that is the outermost orbital. 

300

What is the full electron configuration for the oxygen ion? What is the charge on this ion?

1s²2s²2p⁶

Charge is -2. 

O^2-

400

Draw the full orbital diagram for gallium. 

500

Why do s orbitals fill before d orbitals? Provide the name of this law, and explain it in your own words.

This is due to the Aufbau principle, which states that electrons fill orbitals by energy level--so lower energy levels fill first. 4s has lower energy than 3d, 5s has lower energy than 4d, etc. so these s subshells are filled first. 

Periodic Trends

100

What is Z_eff? What is the periodic trend? 

Z_eff (effective nuclear charge) is the net charge experienced by an outer electron after experiencing shielding from the inner electrons. The pull on outer electrons is weaker due to this shielding. Z_eff increases from left to right across a period because the number of valence electron increases while inner electrons (shielding) stays the same. It decreases down a group because of increasing electron shields. The value of Z_eff is approximately equal to the number of valence electrons. 

200

Nitrogen, Oxygen, and Fluorine are all in the same row of the periodic table. Knowing what you do about atomic radius, ionization energy, and electron affinity, rank these three elements in increasing order for the 3 different trends. 

Atomic radius (decreases across a row): F < O < N (biggest) 

Ionization energy (increases across a row): N < O < F (biggest) 

Electron affinity (increases across a row): N < O < F (biggest) 

300

Rank these in order of increasing size: 

F⁺, F, F^-

F⁺ (smallest) < F < F^- (biggest)

Cations are smaller than their parent atom and anions are larger than the parent atom. 

400

Calcium's 3rd ionization energy is much larger than it's first and second. Why?

Calcium has two valence electrons. Valence electrons are much easier to remove than core electrons, so these come off way easier. The third electron removed from calcium is a core electron, so the ionization energy is much larger. 

500

Provide the likely charge for the ions of these elements: 

Br, Sr, Na

What elements are these ions isoelectronic with? 

Br^- , isoelectronic with Kr

Sr²⁺, isoelectronic with Kr 

Na⁺, isoelectronic with Ar 

Bonding & Naming

100

Identify the following as ionic or covalent:

LiBr

SF₆

CaF₂

LiBr: ionic 

SF₆: covalent

CaF₂: ionic 

200

Provide the formula for the following names: 

sulfate 

strontium chloride 

diphosphorus pentoxide 

Sulfate: SO₃^2-

Strontium chloride: SrCl₂

Diphosphorus pentoxide: P₂O₅

300

What is the charge of iron in the following compound, and how would you write the name of this compound: 

Fe₂O₃

The charge is 3+. Oxygen has a likely charge of 2-, so it is contributing 6-. Iron needs to balance that out, and there are two iron atoms present. 6/2 = 3. 

Iron (III) oxide 

400

What is the bond type in this compound? Is this compound polar? 

EN values: F = 4.0, Br = 2.8  

4.0 - 2.8 = 1.2 

This is a polar covalent bond. This is polar because the lone pairs create t-shaped geometry and the polar bonds do not cancel out. 

500

Draw the polarity arrow for this compound, based on your knowledge of electronegativity trends.

Lewis Structures & Molecular Shapes

100

Draw the lewis structure for ICl₃.

200

What is the octet rule? What are the exceptions?

The octet rule states that atoms want a full outer shell with 8 valence electrons to be most stable. The exceptions are electron deficiency (Boron), hydrogen (only has 2 electrons), an odd number of electrons, and an expanded shell (anything with a d subshell)  

300

Draw the Lewis structure for SCN^-, including any resonance structures. Identify which structure is best using formal charges. 

Hint: the electronegativity of both S & N is 2.5. 

There is no preferred structure, both 1 & 2 work. Since the electronegativity values are the same, the -1 formal charge can be on either. Structure 3 isn't ideal because 2 elements have a non-zero formal charge. 

400

Why do bonds and lone pairs cause deviation from ideal bond angles?

Lone pairs repel the surrounding bonds / electron groups. They take up more space, so they push the other bonds closer together, and alter the ideal bond angle. Multiple bonds cause stronger repulsions than single bonds because they encompass more electrons. 

500

Is this compound polar? 

Polar: asymmetric, there is a net dipole moment

Valence Bond Theory & Hybridization

100

What is the electron geometry and molecular geometry of the following compound: 

EG: octahedral 

MG: square planar 

200

For each of the 5 ELECTRON geometry names we know, provide the hybridization orbitals. 

linear: sp

trigonal planar: sp²

tetrahedral: sp³

trigonal bipyramidal: sp³d

octahedral: sp³d²

300

For the following compound, provide the electron geometry, molecular geometry, and hybridization around the central molecule. 

EG: trigonal bypyramidal 

MG: t-shaped 

Hybridization: sp3d

400

Draw the lewis structure for CH4 and provide the electron geometry, molecular geometry, and hybridization of the central atom. 

EG: tetrahedral 

MG: tetrahedral (the same because there are no lone pairs)

Hybridization of C: sp³

500

What is the electron geometry, molecular geometry, and hybridization of the central atom in SF₄? Draw the lewis structure!

EG: trigonal bipyramidal 

MG: seesaw

Hybridization around S: sp3d