Compounds formed when 2 or more elements react together. The atoms of the element join together by sharing or by transferring electrons to achieve stable electronic structures. Noble gases have stable electronic stuctures.
When atoms of non-metallic elements join together by sharing electrons is called covalent bonding.
When metallic elements and non-metallic elements react together they produce ionic compounds. The metal atoms lose electrons to form positive ions. The atoms of non-metallic elements gain electrons and form negative ions. The oppositely charged ions in the ionic compound and this is called Ionic bonding.
Ionic bonding holds oppositely charged ions together in giant structures. The giant structure of ionic compounds is very regular because the ions pack togrther neatly.
Strong electrostatic forces of attraction act in all directions. Each ion in the structure is surrounded by oppositely charged ion and is held firmly in place.
Sodium Chloride contains equal number of sodium and chloride ions as shown by its formula NaCl. The sodium and chloride ions alternate to form a cube lattice.
Dot and cross diagrams represent the atoms and ions involving in forming ionic bonds. In these diagrams we only show outer most shell of each atom/ion
Non-metals react together = covalent bonding
Simple molecules formed when non-metals can't give away electrons in a reaction, so they share instead; held together by these sharing electrons (very strong)
Sometimes only the same amount of electrons are needed, but otherwise more atoms are involved in the reaction.
Covalent bonding represented like "Venn Diagrams"
Giant covalent structures have large numbers of atoms held together by networks of covalent bonds ( see Giant Covalent Substances)
The elements in a metallic element are all the same size. They form giant structures in which layers of atoms are arranged in regular patterns. You can make models of metal structures by putting lots of small same sized spheres like marbles together.
Metal = giant lattice of metal atoms (or positive ions)
Outer electrons in each atom can move from one to the next
=====> forms a "sea" of delocalised electrons
Strong electrostatic attraction between electrons and positive ions, bonding them together.