What was the copernican revolution?

The Nicolaus Copernicus is the revolutionary mathematician and the astronomer who changed the era by his model of the solar system called the heliocentric model.

Before his time people were living in the time where the geocentric model of the solar system by Ptolemy which stated that earth is the centre of the universe.

But the Copernican heliocentric model proposed that Sun is present at the centre of the universe instead of Earth. This model was not accepted at that time but after experiments of Kepler, the model changed the scientific world.

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.