6. What category of elements is found between the metals and nonmetals on the periodic table?
A synthetic
B. metalloids
C. radioactive
D. noble gases

B. metalloids

Explanation:

The metalloids are found between metals and non-metals on the periodic table.

Metalloids have properties between those of metals and non-metals. Under certain prevalent conditions, they exhibit a set of properties.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.