Chapter 7/8 Quiz

1. In the periodic table, as the atomic number increases from 11 to 17, what happens to the atomic radius?

It remains constant.

It increases only.

It increases, then decreases.

It decreases only.

It decreases, then increases.

As the atomic number increases from 11 to 17 in the periodic table, the atomic radius decreases. This is because as the number of protons in the nucleus increases, the positive charge also increases. This increased positive charge attracts the negatively charged electrons more strongly, causing them to be pulled closer to the nucleus. As a result, the atomic radius decreases.

Explanation

As the atomic number increases from 11 to 17 in the periodic table, the atomic radius decreases. This is because as the number of protons in the nucleus increases, the positive charge also increases. This increased positive charge attracts the negatively charged electrons more strongly, causing them to be pulled closer to the nucleus. As a result, the atomic radius decreases.

2. In which of the following groups are the three species isoelectronic; i.e., have the same number of electrons?

S2-, K+, Ca2+

Sc, Ti, V2+

O2-, S2-, Cl-

Mg2+, Ca2+, Sr2+

Cs, Ba2+, La3+

The species S2-, K+, and Ca2+ are isoelectronic because they all have the same number of electrons. Sulfur (S) has 16 electrons, and when it gains two electrons to become S2-, it has the same number of electrons as potassium (K) and calcium (Ca2+), which both have 18 electrons. Therefore, these three species have the same number of electrons and are isoelectronic.

Explanation

The species S2-, K+, and Ca2+ are isoelectronic because they all have the same number of electrons. Sulfur (S) has 16 electrons, and when it gains two electrons to become S2-, it has the same number of electrons as potassium (K) and calcium (Ca2+), which both have 18 electrons. Therefore, these three species have the same number of electrons and are isoelectronic.

3. Are the most likely to form anions

Noble gases

Alkali metals

Halogens

Transition elements

Actinides

Halogens are the most likely to form anions because they have a high electronegativity and only require one additional electron to achieve a stable electron configuration. Anions are formed when atoms gain electrons, and halogens readily gain one electron to achieve a full outer shell, forming a stable 1- charge. Noble gases do not readily form ions as they have a full outer shell and are already stable. Alkali metals, transition elements, and actinides can form cations by losing electrons, but they are less likely to form anions compared to halogens.

Explanation

Halogens are the most likely to form anions because they have a high electronegativity and only require one additional electron to achieve a stable electron configuration. Anions are formed when atoms gain electrons, and halogens readily gain one electron to achieve a full outer shell, forming a stable 1- charge. Noble gases do not readily form ions as they have a full outer shell and are already stable. Alkali metals, transition elements, and actinides can form cations by losing electrons, but they are less likely to form anions compared to halogens.

4. Of the following electron configurations of neutral atoms, which represents an atom in an excited state?

1s2 2s2 2p5

1s2 2s2 2p5 3s2

1s2 2s2 2p6 3s1

1s2 2s2 2p6 3s2 3p2

1s2 2s2 2p6 3s2 3p5

The electron configuration of an atom in its ground state is the arrangement of electrons in its energy levels. In the given options, the electron configuration 1s2 2s2 2p5 3s2 represents an atom in an excited state because it has an electron in the 3s orbital, which is higher in energy than the 2p orbital. In the ground state, the 3s orbital would be empty. This indicates that the atom has absorbed energy and one of its electrons has moved to a higher energy level.

Explanation

The electron configuration of an atom in its ground state is the arrangement of electrons in its energy levels. In the given options, the electron configuration 1s2 2s2 2p5 3s2 represents an atom in an excited state because it has an electron in the 3s orbital, which is higher in energy than the 2p orbital. In the ground state, the 3s orbital would be empty. This indicates that the atom has absorbed energy and one of its electrons has moved to a higher energy level.

5. The atom that contains exactly two unpaired electrons

S

Ca

Ga

Sb

Br

Sulfur (S) is the correct answer because it has an atomic number of 16, which means it has 16 electrons. The electron configuration of sulfur is 1s2 2s2 2p6 3s2 3p4. In the outermost energy level (3p), there are four electrons, two of which are unpaired. This is because each p orbital can hold a maximum of two electrons with opposite spins. Therefore, sulfur contains exactly two unpaired electrons.

Explanation

Sulfur (S) is the correct answer because it has an atomic number of 16, which means it has 16 electrons. The electron configuration of sulfur is 1s2 2s2 2p6 3s2 3p4. In the outermost energy level (3p), there are four electrons, two of which are unpaired. This is because each p orbital can hold a maximum of two electrons with opposite spins. Therefore, sulfur contains exactly two unpaired electrons.

6. The atom that contains only one electron in the highest occupied energy sublevel.

S

Ca

Ga

Sb

Ga (Gallium) is the atom that contains only one electron in the highest occupied energy sublevel. This can be determined by looking at the electron configuration of each atom. The electron configuration of Ga is [Ar] 3d10 4s2 4p1, which means that the highest occupied energy sublevel is the 4th energy level (4s2 4p1) and it contains only one electron. In contrast, S (Sulfur) has an electron configuration of [Ne] 3s2 3p4, which means that its highest occupied energy sublevel is the 3rd energy level (3s2 3p4) and it contains multiple electrons. Similarly, Ca (Calcium) and Sb (Antimony) also have multiple electrons in their highest occupied energy sublevels.

Explanation

Ga (Gallium) is the atom that contains only one electron in the highest occupied energy sublevel. This can be determined by looking at the electron configuration of each atom. The electron configuration of Ga is [Ar] 3d10 4s2 4p1, which means that the highest occupied energy sublevel is the 4th energy level (4s2 4p1) and it contains only one electron. In contrast, S (Sulfur) has an electron configuration of [Ne] 3s2 3p4, which means that its highest occupied energy sublevel is the 3rd energy level (3s2 3p4) and it contains multiple electrons. Similarly, Ca (Calcium) and Sb (Antimony) also have multiple electrons in their highest occupied energy sublevels.

7. Which of the following statements about atoms is NOT correct?

Atoms are electrically neutral because they have the same number of protons and electrons.

All atoms of a given element must have the same number of protons, neutrons, and electrons.

Most of the volume of an atom contains only electrons.

The nucleus is positively charged.

Almost all of the mass of an atom is in the nucleus.

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Explanation

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8. Which of the following best helps to account for the fact that the F^- ion is smaller than the O^2- ion?

F- has a larger nuclear mass than O2- has

F- has a larger nuclear charge than O2- has

F- has more electrons than O2- has

F- is more electronegative than O2- is

F- is more polarizable than O2- is

The fact that the F- ion is smaller than the O2- ion can be explained by the concept of nuclear charge. The nuclear charge refers to the positive charge of the nucleus, which attracts the negatively charged electrons and determines the size of the ion. Since F- has a larger nuclear charge than O2-, it can attract its electrons more strongly, resulting in a smaller ion size.

Explanation

The fact that the F- ion is smaller than the O2- ion can be explained by the concept of nuclear charge. The nuclear charge refers to the positive charge of the nucleus, which attracts the negatively charged electrons and determines the size of the ion. Since F- has a larger nuclear charge than O2-, it can attract its electrons more strongly, resulting in a smaller ion size.

9. The effective nuclear charge experienced by the outermost electron of Na is different than the effective nuclear charge experienced by the outermost electron of Ne. This difference best accounts for which of the following?

Na has a greater density at standard conditions than Ne.

Na has a lower first ionization energy than Ne.

Na has a higher melting point than Ne.

Na has a higher neutron-to-proton ratio than Ne.

Na has fewer naturally occurring isotopes

The effective nuclear charge experienced by an electron is determined by the number of protons in the nucleus and the shielding effect of inner electrons. Since Na has fewer inner electrons than Ne, the outermost electron in Na experiences a greater effective nuclear charge. This stronger attraction between the nucleus and the outermost electron in Na makes it easier to remove that electron, resulting in a lower first ionization energy compared to Ne.

Explanation

The effective nuclear charge experienced by an electron is determined by the number of protons in the nucleus and the shielding effect of inner electrons. Since Na has fewer inner electrons than Ne, the outermost electron in Na experiences a greater effective nuclear charge. This stronger attraction between the nucleus and the outermost electron in Na makes it easier to remove that electron, resulting in a lower first ionization energy compared to Ne.

10. Which of the following sets of quantum numbers (n, l, m_l, m_s) best describes the valence electron of highest energy in a ground-state gallium atom (atomic number 31) ?

4, 0, 0, 1/2

4, 0, 1, 1/2

4, 1, 1, 1/2

4, 1, 2, 1/2

4, 2, 0, 1/2

The valence electron of highest energy in a ground-state gallium atom (atomic number 31) is in the fourth energy level (n=4), with an angular momentum quantum number of 1 (l=1), a magnetic quantum number of 1 (ml=1), and a spin quantum number of 1/2 (ms=1/2). This combination of quantum numbers is consistent with the electron configuration of gallium, which is [Ar] 3d10 4s2 4p1.

Explanation

The valence electron of highest energy in a ground-state gallium atom (atomic number 31) is in the fourth energy level (n=4), with an angular momentum quantum number of 1 (l=1), a magnetic quantum number of 1 (ml=1), and a spin quantum number of 1/2 (ms=1/2). This combination of quantum numbers is consistent with the electron configuration of gallium, which is [Ar] 3d10 4s2 4p1.