Question

1. what is the shape of the bf₃ molecule?

a. tetrahedral
c. bent
b. pyramidal
d. trigonal planar

1. why is nh₃ pyramidal instead of trigonal planar?

a. it has two unshared pairs of valence electrons on the central atom.
b. it has one unshared pair of valence electrons on the central atom.
c. it has three unshared pairs of valence electrons on the central atom.
d. it has no unshared pairs of valence electrons on the central atom.

1. which of the following elements can form diatomic molecules held together by double covalent bonds?

a. oxygen
c. carbon
b. fluorine
d. nitrogen

1. which of the following pairs of elements is most likely to form an ionic compound?

a. magnesium and fluorine
c. nitrogen and sulfur
b. sodium and aluminum
d. oxygen and chlorine

1. if two fluorine atoms combine to form a molecule, what type of bond will they form?

a. an ionic bond
c. a metallic bond
b. a single covalent bond
d. a double covalent bond

1. the shape of water (h₂o) is ___

a. pyramidal
c. planar
b. bent
d. tetrahedral

1. which molecule below would be a nonpolar molecule?

a. ch₄
c. hcl
b. h₂o
d. nh₃

1. which molecules above in #19 would have hydrogen bonding?

a. ch₄ only
b. h₂o and nh₃
c. h₂o, nh₃ and hcl
d. all of them

Explanation:

• Question 13: BF₃ has 3 bonding pairs and no lone pairs around the central B atom. According to VSEPR theory, it has a trigonal planar shape.
• Question 14: NH₃ has 3 bonding pairs and 1 lone pair around the central N atom. The lone pair - bond pair repulsion causes it to be pyramidal instead of trigonal planar.
• Question 15: Oxygen forms O₂ with a double covalent bond (O = O). Fluorine forms F₂ with a single covalent bond (F - F), carbon forms various bonds but not diatomic with double in this context, nitrogen forms N₂ with a triple covalent bond (N ≡ N).
• Question 16: Magnesium (metal) and fluorine (non - metal) have a large electronegativity difference and form ionic bonds. Sodium and aluminum (both metals) do not form ionic, nitrogen and sulfur (both non - metals) form covalent, oxygen and chlorine (both non - metals) form covalent.
• Question 17: Two fluorine atoms (non - metals) share electrons. They form a single covalent bond (F - F).
• Question 18: H₂O has 2 bonding pairs and 2 lone pairs around the central O atom. According to VSEPR theory, it has a bent shape.
• Question 19: CH₄ is symmetric (tetrahedral) and non - polar. H₂O is bent and polar, HCl is linear (but polar due to electronegativity difference), NH₃ is pyramidal and polar.
• Question 20: Hydrogen bonding occurs when H is bonded to N, O, or F. H₂O (H - O) and NH₃ (H - N) have hydrogen bonding. CH₄ (H - C) and HCl (H - Cl) do not.

Answer:

1. d. trigonal planar
2. b. It has one unshared pair of valence electrons on the central atom.
3. a. oxygen
4. a. magnesium and fluorine
5. b. a single covalent bond
6. b. bent
7. a. CH₄
8. b. H₂O and NH₃