Atomic Structure and the Periodic Table
Atoms have a tiny central nucleus surrounded by negative electrons.
The chemistry of an element is largely determined by the number and arrangement of the electrons in it's atoms.
The number of electrons is equal to the proton number of the atom.
Electrons in Atoms
Electrons in atoms are negatively charged.
The electron shell with the lowest energy fills first until it contains as many electrons as possible, then the next shell starts to fill.
The electronic configuration of an atom is 2, 8, 8 ect. after the first 20 elements it changes slightly.
Each column in the periodic table consists of a group of related elements.
The elements in a group have the same number of electrons in the outer shell.
There are trends in the properties of the elements down a group because of the increasing number of inner full shells
Atoms into Ions
When metals react with non-metals, the metal atoms lose electrons and the non-metals gain electrons.
This produces ionic compounds such as sodium chlorine, Ca+ Cl-.
The properties of an ionic compound are the properties of it's ions, which behave in a different way from the atoms or molecules in the elements.
Atoms want to have full outer shells.
They will either gain or lose electrons to do this.
If an atom has 1,2 or 3 electrons in it's outer shell it will try to lose electrons, wheras if it has 5,6, or 7 electrons in it's outer shell it will try to gain electrons.
If an atom has 4 electrons in it's outer shell it can either gain or lose electrons.
To gain and lose electrons atoms can either do it through ionic bonding (where a non-metal and metal join together and 'swap' electrons so that they each have full outer shells) or through covalent bonding (where atoms 'share' electrons with other atoms.