ATOMS- 1. an atom is the smallest part of a pure substance which retains the _ of that pure substance

COMPOUNDS-
2. atoms of each element are essentially the _

LAW OF DEFINITE PROPORTIONS-
3. this law states that every molecule of a substance contains the _ number of atoms of each element

SOLUTIONS-
4. Solutions are special types of mixtures which are _ so they often can be confused as pure substances

STATES OF MATTER-
5. how would you describe the change in arrangement of particles as heat energy and temperature increases?

6. why does the temperature remain constant during a phase change even though the substance is absorbing heat energy?

7. (number six only)

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 don't see a text, but i am gonna assume this *orbit* the curved path, usually elliptical, described by a planet, satellite, spaceship, etc., around a celestial body, as the sun.