Chapter 4

What is the energy of blue light that has a wavelength of \(450.0 \mathrm{~nm}\) ?

What is the energy of red light with a wavelength of \(660.5 \mathrm{~nm}\) ?

Which type of electromagnetic radiation has a wavelength roughly on the order of the height of a person? What can you say about the energy of this radiation?

Draw a Bohr model for an atom of sulfur (S). How many additional electrons can fit into the \(n=3\) shell?

Why is an electron in a shell that has a low value of \(n\) in a more stable arrangement than one in a shell that has a higher value of \(n\) ?

How many electrons can the \(n=5\) shell in an atom hold?

The ground state for the lithium (Li) atom and the scaled energies of its shells are shown below. Draw a Bohr diagram for the lowest-energy excited state of lithium.

Draw a Bohr diagram for a \(\mathrm{Li}^{+}\) cation in its ground state.

An atom has atomic number 6 and has eight electrons. (a) Which element is this? (b) Is this a neutral atom, a cation, or an anion? If it is an ion, what is its charge? (c) Draw a Bohr diagram for this atom in its ground state.

Use electron-configuration notation to show how electrons are distributed in a ground-state silicon (Si) atom. How many valence electrons does this atom have? Answer: Silicon has atomic number 14, so it has 14 electrons. We start by putting the first two electrons in the 1s subshell, the next two in the 2s subshell, the next six in the \(2 p\) subshell, the next two in the 3s subshell, and the remaining two in the \(3 p\) subshell: \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{2}\) The highest principal quantum number is 3, and summing up the electrons in the two \(n=3\) subshells tells us this atom has four valence electrons.

Without looking at a periodic table, use electron-configuration notation to show how electrons are distributed in a ground-state atom with 33 electrons. How many valence electrons does this atom have? What periodic table group would you expect to find it in? Now look at a periodic table and determine the atom's identity.

Use electron-configuration notation to show how electrons are distributed in a ground-state scandium (Sc) atom.

Using a four-block periodic table as a guide, determine the ground-state electron configuration of copper (Cu). Answer: You should have arrived at \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{9}\), because copper is nine deep into the d block of period 4 . However, copper is one of those exceptions, and its true electron configuration is \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{1} 3 d^{10}\).

Using a four-block periodic table as a guide, determine the ground-state electron configuration of krypton (Kr). Explain why it is proper for this element to be in group VIIIA.

Using a four-block periodic table as a guide, determine the ground-state electron configuration of palladium (Pd).

Write the ground-state electron configuration of radium (Ra), using both the full notation and the noble gas abbreviated notation.

Write the ground-state electron configuration of uranium (U), using both the full notation and the noble gas abbreviated notation.

In which period and which group is the element that has the ground-state electron configuration \([\mathrm{Ar}] 4 s^{2} 3 d^{10} 4 p^{5} ?\) Which element is this? Answer: Rewriting the electron configuration as \([A r] 3 d^{10} 4 s^{2} 4 p^{5}\) to emphasize the valence electrons, we see that the highest value of \(n\) is 4, so this atom is in the fourth period. There are a total of seven valence electrons, and the \(p\) subshell is partially filled, meaning this is a group VIIA element. It is bromine (Br).

In which period and which group is the element that has the ground-state electron configuration \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{3}\) ? Which element is this?

In which period and which group is the element that has the ground-state electron configuration \([\mathrm{Xe}] 6 s^{1} ?\) Which element is this?

Give the full symbol for the atom or ion that has 26 protons and 30 neutrons in its nucleus, and 23 electrons outside its nucleus. Also give the number of the group this element is in.

Give the full symbol for the atom or ion that has eight protons and eight neutrons in its nucleus, and ten electrons outside the nucleus. Also give the name of the group this element is located in.

Predict the chemical formula \(\mathrm{Na}_{\mathrm{}} \mathrm{O}_{y}\) of the compound that results from the reaction between the elements \(\mathrm{Na}\) and \(\mathrm{O}\). Answer: Na is a group IA metal and thus loses one electron to become \(\mathrm{Na}^{+} . \mathrm{O}\) is a group VIA nonmetal and so gains two electrons to become \(\mathrm{O}^{2-} .\) In order for the compound formed to be electrically neutral, the formula must be \(\mathrm{Na}_{2} \mathrm{O}\).

Predict the chemical formula of the compound that results from the reaction between the elements Ba and \(\mathrm{F}\).

Predict the chemical formula of the compound that results from the reaction between the elements \(\mathrm{Al}\) and \(\mathrm{O}\).

Consider X-rays \(\left(\lambda \sim 10^{-10} \mathrm{~m}\right)\) and green light \(\left(\lambda \sim 10^{-7} \mathrm{~m}\right)\) (a) Do a calculation to show how much more energetic X-rays are than green light. (b) Why are X-rays dangerous whereas green light is not?

Light travels extremely rapidly \((c=3.00 \times\) \(\left.10^{8} \mathrm{~m} / \mathrm{s}\right) .\) Suppose you had to travel 30 miles to work every day. If you traveled at the speed of light for the entire trip, how long would it take you to get to work (in seconds)? \([1 \mathrm{mile}=1.61 \mathrm{~km}]\)

According to the equation for the energy of light, which statement is true? (1) The energy of light increases as its wavelength increases. (2) The energy of light decreases as its wavelength increases. Explain how the equation for the energy of light tells you which is true.

The unit of nanometers \((\mathrm{nm})\) is commonly used for the wavelength of visible light. What does \(1.00\) \(\mathrm{nm}\) equal in meters? What does it equal in inches? \([1\) inch \(=2.54 \mathrm{~cm}\) exactly \(]\)

Exposure to gamma rays can kill you, whereas exposure to radio waves is not harmful. Why is this so?

Suppose a radio wave has a wavelength of \(10 \mathrm{~m}\). What is the energy of this radiation (in joules)?

When we say the energy of something is quantized, what does this mean? For what type of objects is energy quantization easily observed?

What is meant by the term quantized energy?

Which is more general, classical physics or quantum physics? Explain your answer.

The fact that electrified atoms emit only certain colors of light in sharp lines, with not all colors blended together, tells us what about an atom?

What type of physics could be used to describe an electron in an atom if the electron could have \(a n y\) energy?

What is another name for a Bohr orbit?

It always takes energy to remove an electron from an atom, no matter what \(n\) shell the electron is in. Also, the higher the \(n\), the more energy an electron starts out with. (a) Explain why it takes energy to remove an electron from an atom no matter what \(n\) shell it is in. (b) Why does it take less energy to remove an electron from an atom the higher its \(n\) value?

What are two things that happen to an electron in an atom as the \(n\) value of the electron increases?

Explain why we construct a Bohr model of the atom by first filling a lower shell to capacity before going to an upper shell.

Why can't an atom's electrons ever be located between orbits?

Use the Bohr model of the atom to explain why saying that an electron can be only at certain distances from the nucleus is the same thing as saying that the electron can have only certain energies.

What is meant by an atom's valence shell?

According to Bohr, why do atoms in the same group in the periodic table have similar chemical properties?

Explain how the Bohr model of the atom accounts for the existence of atomic line spectra.

True or false? It is impossible for the \(\mathrm{H}^{+}\) cation to exist in an excited state. Justify your answer.

What would happen to the electron in a groundstate hydrogen atom if the atom were given \(5.1 \mathrm{eV}\) of energy?

Regarding the representative elements: (a) What does knowing the group number tell you about an element's valence electrons? (b) What does knowing the period number tell you about an element's valence electrons?

The electron in a hydrogen atom relaxes from the \(n=4\) shell to some lower- energy shell. The light emitted during the relaxation has a wavelength of \(1772.6 \mathrm{~nm}\). By calculating the energy of this light, determine the shell to which the electron relaxed. \(\left[1 \mathrm{eV}=1.602 \times 10^{-19} \mathrm{~J}\right]\)

What was the experimental evidence that supported the existence of subshells? Explain how this evidence suggested subshells.