Which of the following bonds can form between atoms of equal electronegativity?
(a) ionic
(b) covalent
(c) hydrogen
(d) van der waals

(D) Van der Waals

Explanation:

Van der Waals forces -

They are the bond that are formed between atoms of the equal electronegativity .

Van der Waals forces are defined as the distance between any two atoms at where the forces becomes repulsive than being attractive .

The process is the resultant of the mutual repulsion between the atoms' electron clouds .

the increase of protons   hope this

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.