The white powder is added to the clear liquid. what event is occurring and is it a physical or chemical change?

The answer to your question is:

Explanation:

What event is occuring?

The white powder is fizzing in contact with the clear liquid.

Chemical change or physical change?

It is a chemical change because of the bubbles we conclude that there is a reaction. All reactions are chemical reactions.

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.