STRUCTURE OF THE ATOM
Atom: - Is a smallest particle of an element that can take place in a chemical reaction.
SUB-ATOMIC PARTICLES
❖ Atoms are made up of three types of particles/sub-atomic particles, namely
i) Protons
ii) Neutrons
iii) Electrons
❖ Protons and neutrons reside in the centre of the atom called the nucleus. The two particles also called nucleons.
❖ The electrons move around the nucleus, each in its own path or orbit.
PROPERTIES OF SUB-ATOMIC PARTICLES
1. PROTON
➢ Has a positive electrical charge
➢ Has an electric charge of +1.6 x 10 -19 C
➢ Has a mass of about 1.6726 x 10 -27 kg
2. NEUTRON
➢ Has no charge
➢ Has a mass of about 1.6749 x 10 -27 kg
➢ It is found inside the nucleus of an atom.
3. ELECTRON
➢ Has a negative electrical charge
➢ Has an electric charge of +1.6 x 10 -19 C
➢ Has a mass of about 9.1094 x 10 -31 kg
➢ It is found outside the nucleus of an atom.
ATOMIC NUMBER
❖ This is the number of protons in the nucleus of an atom.
❖ The atom number is usually written as a subscript before the symbol of the element.
❖ Atomic number identifies a particular element.
MASS NUMBER
❖ This is the total number of protons and neutrons in the nucleus of an atom.
❖ The mass number is written as a superscript before the symbol of the element.
Atomic number = Number of protons
Mass number = Number of protons + Number of neutrons
Number of protons = Number of electrons
❖ Elements also represented by nuclide notation.
ISOTOPY
❖ This is the existence of two or more atoms of the same element having the same atomic number
but different mass number.
ISOTOPES
❖ These are atoms of the same element having the same atomic number but different mass number.
OR
❖ These are atoms of the same element having the same proton number but different neutron number.
ISOTOPES OF HYDROGEN
❖ Hydrogen has three isotopes, these are:-
i) Hydrogen (Normal hydrogen)
ii) Deuterium
iii) Tritium
i) Hydrogen
✓ Has one proton and no neutron
✓ Its mass number is 1
✓ Its symbol is 1H
ii) Deuterium
✓ Has one proton and one neutron
✓ Its mass number is 2
✓ Its symbol is 1H
iii) Tritium
✓ Has one proton and two neutrons
✓ Its mass number is 3
✓ Its symbol is 1H
