Question

Beryllium differs from rest of the members of its family (II A group) in many ways. The reason for this is its (1) small size and high electronegativity. (2) small size and low electronegativity. (3) large size and lower ionization energy. (4) larger size and large ionic radius.

Short answer

The correct option is (1) small size and high electronegativity.

Step-by-step solution

Understand the Family Traits

The II A group, also known as the alkaline earth metals, typically includes elements such as Magnesium (Mg), Calcium (Ca), Strontium (Sr), and Barium (Ba). These elements generally have larger atomic and ionic sizes as you move down the group.

Analyze Beryllium's Unique Characteristics

Beryllium (Be) being the first element in this group, displays unique characteristics due to its position. It has a very small atomic and ionic radius compared to the other members of the II A group.

Understand Electronegativity and Ionization Energy

Electronegativity is a measure of how strongly an atom can attract a bonding pair of electrons. Smaller size and higher electronegativity often go hand in hand. Ionization energy is the energy required to remove an electron from an atom.

Match Characteristics to Beryllium

Beryllium's small size means it has a high charge density, which leads to a higher electronegativity compared to the other group members. It also has relatively high ionization energy, making it less reactive.

Select the Correct Answer

Given Beryllium's unique characteristics of small size and high electronegativity, the correct option is (1) small size and high electronegativity.

Key concepts

alkaline earth metals

The alkaline earth metals are found in Group II A of the periodic table. This group includes elements like Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), and Barium (Ba). These metals share some common properties:

• They have two valence electrons.
• They are highly reactive, although not as much as alkali metals (Group I).
• They have larger atomic and ionic sizes as you move down the group from Beryllium to Barium.

Among these elements, Beryllium stands out due to its significantly smaller size, contributing to its unique characteristics like higher electronegativity and ionization energy compared to its group counterparts. Beryllium's differences can be better understood through core concepts like electronegativity and ionization energy.

electronegativity

Electronegativity is the ability of an atom to attract shared electrons in a chemical bond. It is an essential chemical property that varies across the periodic table:

• Electronegativity tends to increase across a period from left to right.
• It generally decreases as you move down a group.

Beryllium has a high electronegativity compared to other alkaline earth metals. This elevated electronegativity is due to its small atomic size, which allows the nucleus to exert a stronger pull on the shared electrons. Elements with higher electronegativity values are more adept at attracting electrons, influencing their chemical reactivity and bonding characteristics.

ionization energy

Ionization energy is the energy required to remove an electron from an atom in its gaseous state. Important trends can be noted:

• Ionization energy tends to increase as you move across a period from left to right.
• It usually decreases as you move down a group.

Beryllium has a relatively high ionization energy within the alkaline earth metals. This high ionization energy is linked to its small size and high charge density, making it more difficult to remove an electron. As a result, Beryllium is less reactive compared to other members of its group despite being highly reactive in a broader chemical context.

atomic radius

The atomic radius is the distance from the nucleus of an atom to the outermost electron shell. Atomic radius trends help explain various chemical properties:

• Atomic radius decreases across a period from left to right due to an increasing nuclear charge pulling electrons closer to the nucleus.
• It increases down a group as new electron shells are added, making the atoms larger.

Beryllium has a much smaller atomic radius compared to other alkaline earth metals. This small atomic radius is a key factor behind its higher electronegativity and ionization energy. Due to its small size, Beryllium forms stronger bonds with other elements, influencing its unique chemistry within the group.