An unknown substance has the following properties: • A uniform appearance
• Physically separates by boiling
• Is a liquid at room temperature
What type of matter is this unknown substance?
-Heterogeneous mixture
-Element
-Homogeneous mixture
-Compound

Homogeneous mixture

Explanation:

Because mixture can be separated by physical methods and homogeneous are uniformly appearances

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.