Unit 2 check
Unit 2 check: Compound Structure and Properties
10 questions from 7 lessons in Unit 2. Answer each one, and if you miss, follow the link back to where it is taught, then try again. Your score counts first tries.
Question 1 · from 2.1 · Fill the statement
Complete the description of two bonds to hydrogen. The electronegativities are N 3.04, H 2.20 and P 2.19.
An N-H bond is , and the atom in it carries a partial negative charge. A P-H bond is .
Question 2 · from 2.2 · Rank it
Carbon and oxygen are joined by a single bond in methanol, CH₃OH, by a triple bond in carbon monoxide, CO, and by double bonds in carbon dioxide, CO₂. Rank these carbon-oxygen bonds by bond energy.
Largest bond energy first
Give each one a place, 1 for first. Give two the same place if they are equal.
Your ranking: none yet
Question 3 · from 2.3 · Rank it
Ionic radii, in picometers: Li⁺ 76, Na⁺ 102, K⁺ 138, Rb⁺ 152, F⁻ 133, Cl⁻ 181, Br⁻ 196. In a model of each solid, each cation touches its neighboring anions. Rank the four solids by the distance between the centers of a cation and a neighboring anion.
Shortest distance first
Give each one a place, 1 for first. Give two the same place if they are equal.
Your ranking: none yet
Setup for question 4
Yellow brass is an alloy of copper and zinc. Two students are getting ready to draw it.
Question 4 · from 2.4 · Select all
Copper atoms have a radius of about 128 pm and zinc atoms a radius of about 134 pm. Select the two features a particulate model of yellow brass should show.
Select 2 answers, then check.
Setup for question 5
Air is mostly nitrogen, N₂, and oxygen, O₂. The halogens fluorine and chlorine are also made of two-atom molecules, F₂ and Cl₂.
Household bleach is a solution of sodium hypochlorite, NaOCl, which contains the hypochlorite ion, ClO⁻.
Question 5 · from 2.5 · Rank it
Draw the Lewis diagram of each molecule, with every atom reaching 8 electrons. Rank the molecules by the number of electron pairs shared between their two atoms.
Most shared pairs first
Give each one a place, 1 for first. Give two the same place if they are equal.
Your ranking: none yet
Setup for question 6
Some car airbags inflate when sodium azide, a solid made of Na⁺ and N₃⁻ ions, breaks down and releases nitrogen gas. The azide ion, N₃⁻, is three nitrogen atoms in a row with 16 valence electrons. Three Lewis diagrams give every atom 8:
- Diagram A: [N=N=N]⁻, with two lone pairs on each end nitrogen and none on the middle one.
- Diagram B: [N≡N-N]⁻, with one lone pair on the triple-bonded end nitrogen, none on the middle one, and three on the single-bonded end nitrogen.
- Diagram C: [N-N≡N]⁻, the mirror image of B.
Question 6 · from 2.6 · Rank it
Rank diagrams A, B and C of the azide ion as models of the real ion.
Best model first
Give each one a place, 1 for first. Give two the same place if they are equal.
Your ranking: none yet
Setup for question 7
The table summarizes the Lewis diagrams of five molecules. In each one, the central atom is bonded to every F atom by a single bond.
| Molecule | F atoms bonded to the central atom | Lone pairs on the central atom |
|---|---|---|
| BF₃ | 3 | 0 |
| PF₃ | 3 | 1 |
| ClF₃ | 3 | 2 |
| XeF₂ | 2 | 3 |
| BrF₅ | 5 | 1 |
Question 7 · from 2.7 · Fill the statement
Using the table: complete the description.
PF₃ has a molecular geometry, ClF₃ is , and XeF₂ is . The boron atom in BF₃ is hybridized.
Question 8 · from 2.1 · Decide and justify
Calcium fluoride, CaF₂, is a hard solid that melts at 1418 °C, and the melted compound conducts electricity. Is the bonding in calcium fluoride ionic or covalent?
Which reason best supports your claim?
Question 9 · from 2.2 · Decide and justify
Which compound has the stronger attraction between its cation and its anion: sodium fluoride, made of Na⁺ and F⁻, or magnesium oxide, made of Mg²⁺ and O²⁻? The ionic radii are Na⁺ 102 pm, F⁻ 133 pm, Mg²⁺ 72 pm and O²⁻ 140 pm.
Which reason supports your decision?
Setup for question 10
Two more ionic solids to model. These are the ionic radii you need: Li⁺ 76 pm, Ca²⁺ 100 pm and O²⁻ 140 pm.
Question 10 · from 2.3 · Fill the statement
Complete the description of a correct model of one layer of solid lithium oxide. The radius of Li⁺ is 76 pm and the radius of O²⁻ is 140 pm.
The model shows lithium ions for every oxide ion. The oxide ions are drawn than the lithium ions. The closest neighbors of each oxide ion are .
0 of 10 answered.