Oxygen has three isotopes, ¹⁶O, ¹⁷O, and ¹⁸O. The atomic number of oxygen is 8. How many protons and neutrons does each of the isotopes have?

a. How many protons do the following species have?

b. How many electrons does each have?

1. Na⁺
2. Ar
3. Cl^-

Chlorine has two isotopes, ³⁵Cl and ³⁷Cl; 75.77% of chlorine is ³⁵Cl, and 24.23% is ³⁷Cl. The atomic mass of ³⁵Cl is 34.969 amu, and the atomic mass of ³⁷Cl is 36.966 amu. What is the atomic mass of chlorine?

How many valence electrons do the following atoms have?

a. boron

b. nitrogen

Write the ground-state electronic configuration for chlorine (atomic number 17), bromine (atomic number 35), and iodine (atomic number 53).

How many valence electrons do chlorine, bromine, and iodine have?

Look at the relative positions of each pair of atoms listed here in the periodic table. How many core electrons does each have? How many valence electrons does each have?

a. carbon and silicon

b. oxygen and sulfur

Look at the relative positions of each pair of atoms listed here in the periodic table. How many core electrons does each have? How many valence electrons does each have?

c. nitrogen and phosphorus

d. magnesium and calcium

a. Find potassium (K) in the periodic table and predict how many valence electrons it has.

b. What orbital does the unpaired electron occupy?

An atom with a formal charge does not necessarily have more or less electron density than the atoms in the molecule without formal charges. We can see this by examining the potential maps for H₂O, H₃O⁺, and HO⁻.

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a. Which atom bears the formal negative charge in the hydroxide ion?

b. Which atom has the greater electron density in the hydroxide ion?

An atom with a formal charge does not necessarily have more or less electron density than the atoms in the molecule without formal charges. We can see this by examining the potential maps for H₂O, H₃O⁺, and HO⁻.

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c. Which atom bears the formal positive charge in the hydronium ion?

d. Which atom has the least electron density in the hydronium ion?

Give each atom the appropriate formal charge:

a.

b.

Give each atom the appropriate formal charge:

c.

d.

Draw the Lewis structure for each of the following:

d. ⁺C2H5

Draw the Lewis structure for each of the following:

e. CH₃N⁺H₃

Which of the atoms in the molecular models in [Problem 20] have

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a. three lone pairs?

b. two lone pairs?

c. one lone pair?

d. no lone pairs?

Convert the models in Problem 20 to skeletal structures.

a. <IMAGE>

b. <IMAGE>

c. <IMAGE>

d. <IMAGE>

Draw the following orbitals:

a. 3s orbital

b. 4s orbital

c. 3p orbital

Predict whether He₂⁺ exists.

Indicate the kind of molecular orbital (σ, σ*, π, or π*) that results when the two atomic orbitals are combined:

a. <IMAGE>

b. <IMAGE>

a. Which bond would be longer?

b. Which bond would be stronger?

1. C—Cl or C—I

a. Which bond would be longer?

b. Which bond would be stronger?

3. H—Cl or H—F

a. Which bond would be longer?

b. Which bond would be stronger?

2. C—C or C—Cl

Which of the bonds in a carbon–oxygen double bond has more effective orbital–orbital overlap: the σ bond or the π bond?

Draw a Lewis structure for each of the following:

b. CO₃²⁻

Draw the ground-state electronic configuration for each of the following:

a. Mg

Draw the ground-state electronic configuration for each of the following:

b. Ca²⁺

Draw the missing lone-pair electrons and assign the missing formal charges for the following:

a.

b.

Draw the missing lone-pair electrons and assign the missing formal charges for the following:

c.

d.

Explain why the following compound is not stable: