Question

A group of elements in the periodic table is given below (Boron is the first member of the group and thallium is the last.)
Boron
Aluminium
Gallium
Indium
Thallium
Answer the following questions in relation to the above group of elements:
(a) Which element has the most metallic character?
(b) Which element would be expected to have the highest electronegativity?
(c) If the electronic configuration of aluminium is 2, 8, 3, how many electrons will be there in the outermost shell of thallium?
(d) The atomic number of boron is 5. Write the chemical formula of the compound formed when boron reacts with chlorine.
(e) Will the elements in the group to the right of this boron group be more metallic or less metallic in character? Justify your answer.

Answer 1

(a) Thallium, the last element in the group, has the most metallic character.
(b) Among the given elements boron would be expected to have the highest electronegativity.
(c) As aluminium and thallium are in the same group, both of them have the same number of electrons in their outermost shell, that is, three electrons.
(d) The required chemical formula is BCl₃ because boron has three valence electrons and they are shared with three chlorine atoms.
(e) Elements in the group to the right of the boron group have less metallic character because metallic character decreases as we move from left to right in a period, due to increase in ionization energy from left to right in a period.