Structures and Bonding
Nucleus contains (Nucleon) protons (+1) and neutrons (0)
Electrons (-1) orbit the nucleus
Proton no.=Electron no.=Atomic no.
Atomic Mass no.=Proton+Neutron
Arranged in order of atomic no.
Elements react to form compounds by gaining or losing electrons or by sharing e-
Sharing electrons - called covalent bonding (non-metal & non-metal react)
Transferring electrons - called ionic bonding (metal & non-metal react)
Elements in Group 1 react with the elements in Group 7 because Group 1 elements can lose an electron to grain a full outer shell. This electron can be given to an atom from Group 7, which then also gains a full outershell.
THE ARRANGEMENT OF ELECTRONS IN ATOMS
Electrons in atoms are arranged in energy levels or shells.
Due to electron negative charge it is attracted to the postively charge nucleus
Atoms with the same no. of electrons in outershell belong to the same group
No. of e- in outershell of atom shows the way that atoms behave in chemical reactions
Structure and Bonding
Metals and Non-metals react.
Ionic bond is the name of the electrostatic force of attraction.
Ionic bonds between particles results in arrangement of ion that we call giant structure
Reactions can be presented by dot and cross diagrams.
Other elements that can form ionic compounds include those in group 2 & group 6
Nonmetal and Non-metal (sharing electrons)
Giant structures- Diamond- each carbon atom forms 4 covalent bonds
Silicon dioxide and graphite are other examples of Giant structures
BONDING IN METALS
Lattice of metal atoms arranged in regular layers.
Outer electrons form a 'sea' of free electrons surrounding positively charged ions.
sea of electrons are called delocalised electrons which help explain properties
Structures and Properties
It takes a lot of energy to break the bonds which hold a giant ionic lattice together. So ionic compounds have very high melting points - they are all solids at room temperature
Ionic compounds will conduct electricity when we melt them or dissolve them in water because their ions can then move freely.
Substances made up of simple molecules have low melting points and boiling points
The forces between simple molecules are weak. These weak intermolecular forces explain their low melting points and boiling points.
Simple molecules have no overall charge, so they cannot carry electrical charge. Therefore substances cointaining simple molecules do not conduct electricity.
Structures and Properties
GIANT COVALENT SUBSTANCES
Some covalently bonded substances contain giant structures.
These substances have high melting points and boiling points.
The giant structure of graphite contains layers of atoms that can slide over each other which make graphite slippery. The atoms in diamond have a different structure and cannot slide like this - so diamond is a very hard substance.
Graphite can conduct electricity because of the delocalised electrons along its layers.
Carbon molecules having different structures are called fullerenes
GIANT METALLIC STRUCTURES
We can bend and shape metals because the layers of atoms (or…