Taking into account the definition of ionic and covalent bonds, the pair of atoms Br and Cl will share electrons when a bond is formed between them.
Ionic bond
An ionic bond is a type of chemical bond that occurs when one atom gives up an electron to the other, in order for both to achieve electronic stability.
This union normally occurs between metal and nonmetal elements with different electronegativity, which means that the elements have different capacity to attract electrons.
In other words, an ionic bond is produced between metallic and non-metallic atoms, where electrons are completely transferred from one atom to another. During this process, one atom loses electrons and another one gains them, forming ions. Usually, the metal gives up its electrons forming a cation to the nonmetal element, which forms an anion.
Covalent bond
On the other side, the covalent bond is the chemical bond between atoms where electrons are shared, forming a molecule.
Covalent bonds are established between non-metallic elements, such as hydrogen H, oxygen O and chlorine Cl. These elements have many electrons in their outermost level (valence electrons) and have a tendency to gain electrons to acquire the stability of the electronic structure of noble gas. The shared electron pair is common to the two atoms and holds them together.
This case
In this case, considering that K, Li and Ba are metallic atoms and Cl, I and Br are non-metallic atoms, the pair of atoms Br and Cl will share electrons when a bond is formed between them.
Learn more:
linklinklink
link
link
