Question

In group 13, the only metalloid, boron, is at the very top of the group. Explain why the rest of the group has metallic behavior but boron does not. explain the behavior​

Answer 1

Sample Response: All the elements in group 13 have only 3 valence electrons, which means it is a little bit easier for them to lose those 3 electrons than it would be for them to gain 5 to form a full shell. However, it is also easier for elements with fewer electron shells to gain electrons. Since boron only has two electron shells, it is about as capable of gaining electrons as it is of losing electrons, so it behaves as a metalloid. The other elements in this group have more electron shells, so it is much easier for them to lose their valence electrons and they behave like metals.

Answer 2

Boron is considered as metalloid because it shows properties of both metals and non-metals.

Explanation:

Group 13 consists of Boron (B), Aluminium (Al), Gallium (Ga), Indium (In) and Thallium (Tl). All these elements have three valence electrons which means the outermost shell has three electrons for all these three elements.

• Having 3 electrons, all elements should display electropositive property. But Boron here becomes an exception and displays an electronegative property.
• Boron shows non-metallic property because it combines with electropositive atoms like Sodium (Na) or Potassium (K). Also, boron shows non-metallic property by forming covalent boron hydrides.
• Boron shows metallic property because it combines with Fluorine to form $BF_{3}$.  Boron ion forms borderline acid as $BH_{3}$ is a soft acid and $BF_{3}$ is a strong acid.

Properties of exceptional boron element:

• Boron is the lightest element with the smallest size.
• Boron mounts special aggregates that contain multicentre bonds whereas other elements of the same group models a metallic grid with delocalized valence electrons.
• Boron has high ionization energy.
• Boron has low electron affinity and low electronegativity.