Which is not a characteristic of an Ammonite? They are the most widely known fossil
They lived on the land 240-65 million years ago
Became extinct with the dinosaurs
Have a solid external shell

true

hope that

tracks, burrows, eggshells, nests, tooth marks, or gastroliths

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.