- The nucleus of an atom is made of protons and neutrons.
- Protons have a positive charge, electrons a negative charge and neutrons not charged.
- The atomic number(or proton number) of an element is equal to number of protons in the nucleus of its atoms.
- Elements are arranged in order of their atomic numbers in the periodic table.
- The mass number is the sum of the protons and neutrons in the nucleus of an atom
The arrangement of electrons in atoms
- The atoms of the unreactive noble gases…