Question

What would the charge on an ion of boron be?

Answer 1

Some chemical elements do not have completely filled electrons in their subshells and try to attain the nearest noble or inert gas configuration by either losing or gaining electrons. After the gaining or losing of electrons, these elements turned to be ions by carrying charge, either positive or negative with the number of electrons lost or gain can be called as the charge of the ion.

Complete answer:
Periodic table is the representation of chemical elements of a total of $118$ chemical elements. These all are arranged in vertical columns and horizontal rows, the vertical columns are called groups and horizontal rows are called periods. There are a total of $7$ periods and $18$ groups in the periodic table.
Boron is the element with atomic number $5$ and belongs to group $13$. The number of electrons in a boron atom are $5$, the number of valence electrons in a boron atom are $3$.
The boron atom tries to get stability. To get stability it has to attain neon gas configuration by gaining $5$ electrons, or has to lose $3$ electrons to get helium gas configuration. It is easier for the loss of $3$electrons than gaining of $5$ electrons.
Thus, boron loses three ions and becomes ${B^{ + 3}}$, the charge on boron would be $+ 3$.

Note:
Metals easily lose electrons, metallic character decreases down the group. In group $13$, boron is a first element and also only metal in that group. Thus, it tries to lose electrons rather than gaining electrons to get stability by attaining the electronic configuration of the nearest noble gas.