Question

Identify each of the following elements: a. a member of the same family as oxygen whose most stable ion contains 54 electrons b. a member of the alkali metal family whose most stable ion contains 36 electrons c. a noble gas with 18 protons in the nucleus d. a halogen with 85 protons and 85 electrons

Short answer

The identified elements are: a. Tellurium (Te) b. Rubidium (Rb) c. Argon (Ar) d. Astatine (At)

Step-by-step solution

Identify element with 54 electrons and the same family as oxygen

First, we know that oxygen is in Group 16 of the periodic table. An element in the same family as oxygen will also be in Group 16. We are also given that the most stable ion of this element has 54 electrons. We should look for an element in Group 16 that forms an ion with 54 electrons. The most common ion formed by elements in Group 16 is the \(2^{-}\) ion, meaning they gain 2 electrons. To find the neutral element that forms this ion with 54 electrons, we would subtract 2 from the number of electrons in the ion, giving us a neutral element with 52 electrons. An element with 52 electrons has an atomic number of 52, which is tellurium (Te).

Identify the alkali metal with a stable ion containing 36 electrons

Alkali metals are found in Group 1 of the periodic table. The most common ion formed by alkali metals is the \(1^{+}\) ion, meaning they lose 1 electron. To find the neutral alkali metal that forms an ion with 36 electrons, we add 1 to the number of electrons in the ion, giving us a neutral element with 37 electrons. An element with 37 electrons has an atomic number of 37, which is rubidium (Rb).

Identify the noble gas with 18 protons

Noble gases are found in Group 18 of the periodic table. All noble gases are chemically inert due to their full valence electron shells. An element with 18 protons has an atomic number of 18. Looking at the periodic table, an atomic number of 18 corresponds to argon (Ar), which is a noble gas.

Identify the halogen with 85 protons and 85 electrons

Halogen elements are found in Group 17 of the periodic table. We are given that the halogen has 85 protons and 85 electrons. This means the atomic number of the element is 85. Browsing the periodic table, we find the element with an atomic number of 85 is astatine (At), which is a halogen. So, the elements identified are: a. Tellurium (Te) b. Rubidium (Rb) c. Argon (Ar) d. Astatine (At)

Key concepts

Group 16 Elements

The Group 16 elements, also known as chalcogens, occupy a distinct place in the periodic table. These elements include oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive polonium (Po). One key characteristic is their ability to form ions by gaining two electrons, resulting in a stable 2^- charge.

For instance, when an element from this group forms an ion, it typically gains two electrons to achieve a noble gas electron configuration, which is particularly stable. This is because elements strive to complete their outer electron shells, emulating the inertness of noble gases. Therefore, the exercise example of tellurium (Te) gaining two electrons to form an ion with 54 electrons is reflective of this tendency to seek a complete valence shell. Understanding the behavior of Group 16 elements is crucial in predicting their reactions and bonding patterns with other elements.

Alkali Metal Ions

Alkali metals, located in Group 1 of the periodic table, are highly reactive due to their single valence electron which they readily lose to form 1+ ions. This includes elements like lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

The alkali metals react vigorously with nonmetals, particularly halogens, to form ionic compounds. In the Rubidium (Rb) example from our exercise, by losing one electron to form a Rb1+ ion with 36 electrons, Rb achieves the electron configuration of krypton, a noble gas. Recognizing the predictable ion formation of alkali metals is essential for understanding chemical reactions involving these elements.

Noble Gas Electron Configuration

Noble gases are the Group 18 elements of the periodic table and are characterized by their complete valence electron shells, which make them exceptionally stable and inert. Their electron configuration is the benchmark for stability that other elements attempt to achieve through the gain or loss of electrons.

For example, argon (Ar), the noble gas with 18 protons as noted in the exercise, has a full outer shell of electrons, making it unreactive. The noble gas electron configuration is a crucial concept in chemistry as it underpins the octet rule, which states that atoms tend to form compounds in ways that give them eight valence electrons, similar to the electron structure of noble gases.

Halogen Elements

Halogens, found in Group 17 of the periodic table, are non-metallic elements that include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Halogens are highly reactive, particularly with alkali metals and alkaline earth metals, due to their one electron short of a noble gas configuration.

These elements form 1- ions by gaining an electron, evidenced by astatine (At) with its 85 protons and 85 electrons. Astatine, like all halogens, has seven valence electrons and only needs one more to reach the coveted stability of the noble gases. Recognizing halogens is important due to their significant role in various chemical reactions and their common occurrence in organic and inorganic compounds.