THE PARTICLES OF MATTER (PART I): ATOMS
Atoms: electrically balanced particles that consist in one positively charged centre called the nucleus surrounded by a cloud of negatively charged particles called the electrons, to exactly balance the nuclear charge.
Molecules: electrically balanced particles with more than one positive centre (nuclei). Molecules are sets of bonded atoms that act as a unit.
Ions: atoms (or groups of atoms) with unbalanced charge.
As it can be appreciated, atoms seem to be the essential particles for any kind of matter. They were thought to be the simplest possible particles, with no possibility of having parts or being broken.
Atomic and Mass Numbers
Nr of protons = ATOMIC NUMBER of the atom ( Z )
The atomic number is also given the more descriptive name of proton number.
The number of protons will determine the number of electrons necessary to balance the atoms charge.
Nr of protons + Nr of neutrons = MASS NUMBER of the atom ( A ) - The mass number is also called the nucleon number.