WhyA covalent bond is a shared pair of electrons between two atoms, held together by the electrostatic attraction between the shared electrons and both nuclei.
2Multiple choice · Easy
What is the shape and bond angle of a methane ($\text{CH}_{4}$) molecule?
Tetrahedral, $109.5^{\circ}$
Trigonal planar, $120^{\circ}$
Linear, $180^{\circ}$
Bent, $104.5^{\circ}$
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WhyWith 4 bonding pairs and no lone pairs around carbon, VSEPR predicts a tetrahedral shape with bond angles of $109.5^{\circ}$.
3Multiple choice · Medium
What is the molecular shape of ammonia, $\text{NH}_{3}$?
Trigonal pyramidal
Trigonal planar
Tetrahedral
Linear
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WhyNitrogen has 3 bonding pairs and 1 lone pair (4 electron domains). The lone pair gives a trigonal pyramidal shape with bond angles of about $107^{\circ}$.
4Multiple choice · Medium
Which element is the most electronegative?
Oxygen
Chlorine
Fluorine
Nitrogen
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WhyFluorine is the most electronegative element; electronegativity increases across a period and up a group, placing F at the top right (excluding noble gases).
5Multiple choice · Medium
What is the strongest intermolecular force between water molecules?
London (dispersion) forces
Dipole-dipole forces
Hydrogen bonding
Ionic bonding
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WhyWater molecules have O bonded to H and lone pairs on O, allowing hydrogen bonding, the strongest of the intermolecular forces present.
6Multiple choice · Hard
Which molecule is non-polar overall even though it contains polar bonds?
$\text{H}_{2}\text{O}$
$\text{CO}_{2}$
$\text{NH}_{3}$
$\text{HCl}$
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Why$\text{CO}_{2}$ is linear and symmetrical, so the two equal and opposite bond dipoles cancel, giving a non-polar molecule. $\text{H}_{2}\text{O}$, $\text{NH}_{3}$ and $\text{HCl}$ are polar.
7Fill in the blank · Easy
The number of shared (bonding) electron pairs in a nitrogen molecule, $\text{N}_{2}$, is .
Answer:
3 / three
Why$\text{N}_{2}$ contains a triple bond, which is 3 shared pairs of electrons.
8Fill in the blank · Medium
The bond angle in a carbon dioxide molecule, $\text{CO}_{2}$, is degrees.
Answer:
180 / 180 degrees
Why$\text{CO}_{2}$ has 2 electron domains (2 double bonds) and no lone pairs on carbon, giving a linear shape with a bond angle of $180^{\circ}$.
9Multiple choice · Medium
BF3 and AlCl3 are both trigonal planar molecules. What does this indicate about the central atom?
It has three bonding pairs and no lone pairs
It has four bonding pairs
It has two bonding pairs and two lone pairs
It has three bonding pairs and one lone pair
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WhyA trigonal planar shape arises from three bonding pairs and no lone pairs on the central atom.
10Multiple choice · Medium
The bond angle in a trigonal planar molecule is approximately
120 degrees
104.5 degrees
109.5 degrees
107 degrees
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WhyThree electron domains repel to 120 degrees.
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