BP Periodic Structure and Trends

Question 1

Which of the following elements are found in the same group? Select all that apply.

• Boron
• Carbon
• Nitrogen
• Phosphorus
• Arsenic

Answer 1

Nitrogen, phosphorus, arsenic

Question 2

Match each of the following elements with their proper classification.

Answer 2

Question 3

Alkali metals are characterized by which of the following? Select all that apply.

• Reactivity with water
• Ability to act as strong reducing agents
• Ability to form strong acids when bound with hydrogen
• A single valence electron in their ground state

Answer 3

• Reactivity with water
• Ability to act as strong reducing agents
• A single valence electron in their ground state

Alkali metals are located in the first column of the periodic table; they include sodium and potassium. These metals are highly reactive with water.

Due to their extreme tendency to lose a single electron and reach a noble gas configuration, alkali metals serve as good reducing agents.

Alkali metals have a single valence electron in their ground state.

Question 4

True or false: Many transition metal elements can typically be found with multiple possible oxidation states.

Answer 4

This statement is true. The number of electrons a transition metal can lose varies, so most have multiple oxidation states. For example, iron (Fe) is most commonly found with oxidation numbers of +2 or +3, although states from −2 to +6 are possible.

Question 5

Identify the element below that belongs in the halogen group.

• Carbon
• Nitrogen
• Oxygen
• Fluorine

Answer 5

Fluorine

Fluorine is in group 17 and is a halogen.

Question 6

Which of the following elements are noble gases? Select all that apply.

• Hydrogen
• Helium
• Xenon
• Iodine

Answer 6

Helium, Xenon

Question 7

Choose the element below that would have the highest effective nuclear charge.

• Boron
• Carbon
• Nitrogen
• Oxygen

Answer 7

Oxygen

Zeff increases across a period because of the increased number of protons in the nucleus, so oxygen has the highest effective nuclear charge of the options presented here.

Question 8

Of the atoms listed below, which one will have the largest atomic radius?

• K
• K⁺
• Mg
• Mg²⁺

Answer 8

K

Atomic radius increases as you move down and to the left along the periodic table. Therefore, potassium will generally have a larger radius than magnesium. However, be careful when dealing with charged species. Potassium that has been ionized has lost an electron, gaining the electron configuration of argon. This causes its effective nuclear charge to be distributed over fewer electrons, pulling them closer and reducing the radius of the ion. The uncharged species is thus larger than K+.

Question 9

Answer 9

Alkali Metals

The figure shows successive ionization energies for an unknown element. The first IE value is very small, indicating that it is very easy for this element to lose a single electron. However, the second ionization energy is higher than any other, implying that removing a second electron is energetically unfavorable. We can conclude that this electron is being removed either from a full or half- filled orbital. Alkali metals fit this trend; after the first ionization they have reached noble gas configuration, so the removal of a second electron would disturb a complete octet and is highly energetically costly.

Question 10

Answer 10

• Potassium
• Silicon
• Phosphorus
• Nitrogen
• Oxygen

Question 11

What would increase the Zeff of an atom?

Answer 11

More protons in the nucleus; More non-valence electrons

Question 12

As you move to the ______ on the periodic table, Zeff increases; as you move ______ the periodic table, Zeff increases.

Answer 12

right, up

Question 13

Rank the following elements in order of increasing atomic radius.

• Nitrogen
• Sodium
• Boron
• Fluorine
• Potassium

Answer 13

Fluorine

Nitrogen

Boron

Sodium

Potassium

Question 14

Rank the following species in order of increasing atomic/ionic radius.

• Na⁺
• Cl^-
• Na
• Cl

Answer 14

Cl

Cl^-

Na⁺

Na

For elements that form cations, the ionic radius is typically smaller than the atomic radius. For elements that form anions, the ionic radius is typically larger than the atomic radius. Atomic radius also decreases as you go across the periodic table. Thus, the correct order is Cl, then Cl-, then Na+, and finally Na.

Question 15

True or false: Ionization energy refers to the energy released when an element loses a valence electron.

Answer 15

This statement is false. Ionization energy refers to the energy required to free a valence electron from an element.

Question 16

Rank the following elements in order of increasing first ionization energy.

• Magnesium
• Chlorine
• Sodium
• Sulful

Answer 16

Sodium

Magnesium

Sulfur

Chlorine

Ionization energy increases as you move across a period and decreases as you move down a group. Therefore, the correct order is sodium, then magnesium, then sulfur, and finally chlorine.

Question 17

Which choice is an accurate statement about electron affinity?

• It reflects an endothermic process for both bromine and potassium
• It an exothermic process for both bromine and potassium
• The process that it reflects is endothermic for bromine but exothermic for potassium
• The process that it reflects is exotheric for bromine but endothermic for potassium

Answer 17

The process that it reflects is exotheric for bromine but endothermic for potassium

To establish a complete octet, bromine needs only one additional electron. Therefore, when bromine gains an electron, it will become more stable and release energy. Potassium, in contrast, prefers to lose an electron to have a full octet. For this element, adding another electron is unfavorable and will require energy, making it an endothermic process.

Question 18

Rank the following elements in order of increasing electron affinity.

• Bromine
• Fluorine
• Iodine
• Chlorine

Answer 18

Iodine

Bromine

Chlorine

Fluorine

Atoms closer to the top right of the periodic table have higher electron affinity values. Therefore, the correct order is iodine, then bromine, then chlorine, then fluorine.

Question 19

When more electronegative elements are in covalent bonds with less electronegative elements, the ______ density tends to be focused around the ______ electronegative of the two elements.

Answer 19

electron; more

More electronegative elements tend to pull electron density toward themselves when participating in bonds.

Question 20

Rank the following elements in order of increasing electronegativity.

Oxygen

Carbon

Sodium

Fluorine

Lithium

Answer 20

Sodium

Lithium

Carbon

Oxygen

Fluorine

Question 21

True or false: All noble gases have eight valence electrons.

Answer 21

This statement is false. While all noble gases do have a completely filled valence shell, helium only has two valence electrons. Below helium, however, all noble gases have eight valence electrons.

Question 22

Rank the following elements in order of increasing second ionization energy.

• Beryllium
• Magnesium
• Sodium
• Calcium

Answer 22

Calcium

Magnesium

Beryllium

Sodium

Ionization energy increases as you move across a period and decreases as you move down a group. Calcium, magnesium, and beryllium all need to lose two electrons to reach a noble gas configuration, so their second ionization energies are relatively low. Sodium’s second ionization energy is high because sodium only needs to lose a single electron to attain a noble gas configuration. As a result, it would take a lot of energy for Na+ to lose another electron. Therefore, the correct order is calcium, then magnesium, then beryllium, and finally sodium.