Chapter 4

(a) What is the numbering system used to label shells? (b) What is the lettering system used to label subshells? (c) How many subshells are there in a given shell?

How many electrons can each subshell hold before it is considered full?

Bohr solved the potassium problem by putting its last electron where? How did he justify this?

Write the electron configuration for the following elements without using the noble gas abbreviated form (use the periodic table to assist you). (a) \(\bar{B}\) (b) \(\mathrm{Sc}\) (c) \(\mathrm{Co}\) (d) Se (e) \(\mathrm{Ru}\)

In which period and group in the periodic table are these atoms found? (a) \(1 s^{2} 2 s^{2} 2 p^{3}\) (b) \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{1}\) (c) \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{10} 4 p^{5}\)

A student has written what he thinks are some ground-state electron configurations. Which ones have something wrong with them? What is wrong? (a) \(1 s^{2} 2 p^{6} 3 s^{1}\) (b) \(1 s^{2} 2 s^{6} 3 s^{2} 3 p^{6} 4 s^{2} 4 p^{6}\) (c) \(2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{7}\) (d) \(1 s^{2} 2 s^{2} 2 p^{7} 3 s^{3} 3 p^{6}\) (e) \(1 s^{2} 2 s^{2} 2 p^{5} 3 s^{1}\) (f) \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{10} 4 p^{6} 5 s^{1} 4 d^{4}\) [This is the transition metal niobium, which violates the four-block electron-assignment rules, so be careful.]

How many valence electrons does each of these atoms have? (a) \(1 s^{2} 2 s^{2} 2 p^{3}\) (b) \(1 s^{2} 2 s^{1}\) (c) \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{7}\) (d) \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6}\) (e) \(1 s^{2}\)

Regarding primary quantum number \(n\), which representative elements have valence electrons with an \(n\) value that is three times the \(n\) value of lithium's valence electrons? What period are they in?

Write electron configurations for \(\mathrm{O}, \mathrm{O}^{2+}\), and \(\mathrm{O}^{2-}\). Which form would you expect to find in most compounds of oxygen? Why?

When using the periodic table to assign electron configurations, what is the rule for the \(n\) quantum number when you are in the \(d\) block? When you are in the \(f\) block?

Why are the \(s, p, d\), and \(f\) blocks in the periodic table \(2,6,10\), and 14 blocks wide, respectively?

(a) According to the Bohr model, why might someone expect that atoms would not change in size as you go from left to right across a period? (b) In fact, atoms do change in size across a period. What is the trend and what is the explanation for it?

According to the Bohr model, why do atoms get larger as you proceed down a group in the periodic table?

Which atom has a smaller 1s subshell, lithium (Li) or beryllium (Be)? Justify your answer.

Which atom has a smaller valence shell, lithium (Li) or sodium (Na)? Explain your answer.

Which atom is larger, lithium (Li) or beryllium (Be)? Explain your answer.

Which atom is larger, lithium (Li) or sodium (Na)? Explain your answer.

As you move from left to right across a period you add more subatomic particles to the atoms, and yet the atoms become smaller. (a) What subatomic particles are you adding? (b) If you are adding particles, why don't the atoms become larger?

Order the following atoms from smallest to largest, judging from their relative positions in the periodic table: \(\mathrm{Cs}, \mathrm{Fe}, \mathrm{Ti}, \mathrm{Hf}\)

Order the following atoms from smallest to largest, judging from their relative positions in the periodic table: \(\mathrm{Ca}, \mathrm{Se}, \mathrm{F}, \mathrm{S}\).

Explain the trends in ionization energy in terms of the trends in atomic aize.

What is the octet rule, and what is the justification behind it?

How do metal atoms usually attain an octet in chemical reactions?

How do nonmetal atoms usually attain an octet in chemical reactions?

Draw the Bohr model for a \(\mathrm{Cl}\) atom and for a \(\mathrm{Cl}^{-}\) ion. How many electrons are there in the valence shell in each drawing?

Draw a Bohr model for an Al atom and for an \(\mathrm{Al}^{3+}\) ion. How many electrons are there in the valence shell in each drawing?

Predict the formula of the compound that forms when sodium atoms react with sulfur atoms. Completely explain your reasoning.

Predict the formula of the compound that forms when lithium atoms react with nitrogen atoms. Completely explain your reasoning.

Why are roman-numeral group numbers for the representative elements useful in predicting how many electrons an atom will gain or lose in a chemical reaction?

When a group IIA element \(X\) reacts with a group VIIA element \(Y\), what will be the formula? Why?

Explain what is meant by this statement: The element hydrogen is an exception to the octet rule and yet it obeys it in principle.

Aluminum forms compounds with both sulfur and oxygen. Why are the formulas of the resulting compounds \(\mathrm{Al}_{2} \mathrm{~S}_{3}\) and \(\mathrm{Al}_{2} \mathrm{O}_{3}\), respectively? Why are the formulas similar?

True or false? The \(\mathrm{O}^{2-}\) and \(\mathrm{F}^{-}\) anions have identical electron configurations. Justify your answer with Bohr diagrams and electron configuration notation.

Which part of the following statement is true and which part is false? \(\mathrm{Mg}^{2+}\) and \(\mathrm{Na}^{+}\) have identical electron configurations, and they also have similar properties. Explain your answer fully.

How can you tell how many electrons a representative metal is likely to lose? What, in general, will be the charge of the cation it forms?

How can you tell how many electrons a representative nonmetal is likely to gain? What, in general, will be the charge of the anion it forms?

Consider an anion and a cation joining to form a compound. (a) How does knowing the charge of the ions help to determine the formula? (b) What would be the formula of the compound formed from \(\mathrm{Ca}^{2+}\) cations and \(\mathrm{N}^{3-}\) anions?

What is wrong with Bohr's planetary model of atomic electrons according to modern quantum mechanical theory? (Hint: Use Heisenberg's uncertainty principle in your answer.)

Quantum mechanical tunneling is one consequence of quantum theory. What is quantum mechanical tunneling?

What is an orbital?

Draw an s orbital, a \(p\) orbital, and a \(d\) orbital.

What gave Schrödinger justification to think of an electron in an atom as a nebulous cloud?

How many seconds does it take light to travel \(3.00 \times 10^{3}\) miles from New York to California? \([1\) mile \(=1.61 \mathrm{~km}]\)

A laser emits a beam of green light that has a wavelength of \(5.00 \times 10^{-5} \mathrm{~cm} .\) What is the wavelength of this light in nanometers?

What is the wavelength in nanometers of infrared light for which \(\lambda=2.50 \times 10^{-5} \mathrm{~m}\) ? How many times longer is this wavelength than red light that has a wavelength of \(750 \mathrm{~nm}\) ?

Electromagnetic radiation emitted by magnesium has a wavelength of \(285.2 \mathrm{~nm}\). (a) Is this radiation visible to the eye? (b) What is the energy of this radiation?

Would moving an electron farther from an atom's nucleus give off light energy or require the absorption of light energy? Explain your answer.

According to Bohr's model, is energy absorbed or released when an electron moves to a shell of lower \(n\) ?

According to Bohr's model, energy must be put into an atom to move an electron from a low-energy shell to a higher-energy shell. How do you calculate the amount of energy needed for the move?

According to Bohr, what is so special about the valence shell of an atom?