Two groups of seventh graders were tested to compare thwir speed solving integer problems. one group had calculators, the others didn't. which is the dependent variable, independent variable and the control variable.

the control variable is the group that isn't using calculators as we're comparing the calculator group with the other. the dependent variable is the speed or time they take to do the integer problems as their time changes when using a calculator or not. the independent variable is whether they have calculators or not as it's a variation but it doesn't depend on any other variable.

the volume increases

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.