Which of the following is a chemical property? density melting point solubility toxicity

Toxicity

Explanation:

Chemical property is defined as the property of a substance which becomes evident during chemical change in which a change in chemical composition takes place. A new substance is formed in these reactions. Example: Toxicity

Physical property is defined as the property of a substance which becomes evident during physical change in which there is alteration in shape, size etc. No new substance gets formed during physical change. Example: Density, Melting point, Solubility

Thus the chemical property is toxicity.

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.