LIFE SCIENCE

Detailed explanation-1: –An atom X has 12 protons and 12 electrons, this means it is neutral right now and its atomic number is 12 (as total number of protons is equal to the atomic number of the atom).

Detailed explanation-2: -The symbol for magnesium is . Magnesium has an atomic number of 12 and a mass number of 24. So a magnesium atom has 12 protons, 12 electrons, and 12 neutrons. Elements in the same period have the same outermost energy level, also called the valence shell.

Detailed explanation-3: -Explanation: The atomic number of magnesium is 12. Its nucleus must contain 12 protons and no electrons.

Detailed explanation-4: -A neutral atom of Carbon-12 contains six protons, six neutrons, and six electrons; therefore, it has a mass number of 12 (six protons plus six neutrons).

Detailed explanation-5: -As both X and Y had 12 protons both has atomic number 12 that is magnesium.