The sum of protons, neutrons and electrons in the 27Al atom is.

The number of protons and electrons are equal to each other and equal to the number of the element in the periodic table. Protons have a positive charge and are written with a plus sign. Electrons have a negative charge and are written with a minus sign. The protons are balanced by the electrons so that the atom has a neutral charge, zero charge.

AL number 13. So protons p = +13, electrons e = – 13.

To find the number of neutrons it is necessary to subtract protons from the mass of aluminum equal to 27.

n = 27 – 13 = 14

Neutrons are neutral and have no sign.

Answer: protons p = +13, electrons e = – 13, neutrons n = 14.