The elements in group 17 of the periodic table are all called halogens. all halogens have the sameatomic number. atomic mass. number of possible isotopes. number of valence electrons.

They have the same number of valence electrons

Explanation:

The groups on the periodic table are the vertical lines of groups. In group 18 the elements are known as noble gases. They have all 8 valence electrons. As you go to the left the groups have one less valence electron. Group 17 has 7 valence electrons.

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.  

i'm pretty sure it is letter c.) car