Problem 14 - Chemistry The Central Science In Si Units

Question

Consider the elements \(\mathrm{Ba}, \mathrm{Na}, \mathrm{O}, \mathrm{B}, \mathrm{P},\) and \(\mathrm{Kr}\). From this list, select the element that (a) is most electronegative, (b) has the greatest metalliccharacter, \((\mathbf{c})\) most readily forms a positive ion, \((\mathbf{d})\) exhibits a maximum oxidation sate of +5 , (e) exists as monoatomic gas at room temperature, (f) has multiple allotropes.

Step-by-Step Solution

Answer

(a) O, (b) Ba, (c) Na, (d) P, (e) Kr, (f) B.

Step 1: Determine Most Electronegative Element

Electronegativity is the ability of an atom to attract electrons towards itself. Among the elements given, oxygen (O) is the most electronegative.

Step 2: Identify Element with Greatest Metallic Character

The metallic character increases as you move down a group in the periodic table, and decreases as you move from left to right across a period. Barium (Ba) has the greatest metallic character among the given elements.

Step 3: Determine Element Forming Positive Ion Readily

Elements that are more metallic tend to lose electrons and form positive ions easily. Sodium (Na) forms positive ions most readily.

Step 4: Identify Element with Maximum Oxidation State of +5

Phosphorus (P) is known to have a maximum oxidation state of +5.

Step 5: Find Element Existing as Monoatomic Gas

At room temperature, noble gases exist as monoatomic gases. Therefore, krypton (Kr) exists as a monoatomic gas.

Step 6: Determine Element with Multiple Allotropes

Elements with multiple allotropes can exist in different structural forms. Boron (B) has multiple allotropes.

Key Concepts

Electronegativity

Electronegativity is a fundamental concept in chemistry that describes an atom's ability to attract and hold onto electrons when it forms a chemical bond. The higher the electronegativity, the stronger the atom can pull electrons toward itself. In the periodic table, electronegativity generally increases as you move from left to right across a period and decreases as you move down a group.
Among the elements you are considering, oxygen (O) is the most electronegative. This means oxygen is highly effective at attracting electrons. This property is crucial for its role in water formation and many other chemical reactions, where it often forms polar bonds by pulling electrons toward itself.

Metallic Character

The metallic character of an element refers to how easily it can lose electrons to form positive ions, commonly known as cations. Elements with a strong metallic character are shiny, conductive, and are typically metals.
In the periodic table, the metallic character increases as you move down a group and decreases as you move from left to right across a period. Among the elements provided, barium (Ba) shows the greatest metallic character. This makes barium a classic metal, capable of easily losing electrons and engaging in metallic bonding.

Oxidation States

Oxidation states are indications of the degree of oxidation of an atom in a chemical compound. They represent the number of electrons an atom gains or loses when forming a compound.
An element can have multiple oxidation states, but some have a maximum state where they reach their most stable form. Phosphorus (P) exhibits a maximum oxidation state of +5. This is observed in compounds like phosphorus pentoxide (P5) and is a vital property for its reactivity in chemical processes and its role in chemical fertilizers.

Allotropes

Allotropes are different structural forms of the same element. Allotropes arise due to the different ways atoms can be bonded together, resulting in distinct physical and chemical properties.
Boron (B) is an element known to have multiple allotropes. These different forms contribute to boron's versatility in various applications, such as in materials science and chemistry. For example, boron can be found in forms ranging from amorphous powder to crystalline boron, each with unique characteristics.

Noble Gases

Noble gases are a group of elements noted for their lack of reactivity and the fact that they exist as monoatomic gases at room temperature. Characterized by a full valence shell, they do not easily form compounds and are very stable.
Among the provided elements, krypton (Kr) is a noble gas and thus exists naturally as a monoatomic gas at room temperature. This inert characteristic makes noble gases useful in applications where a non-reactive environment is desired, such as in lighting and in gas-filled insulation.