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CHEM what you need to know 1 (types of materials (pure substances-…
CHEM what you need to know 1
types of materials
heterogenus- mixture that is not uniform in composition
homogenus- solid, liquid, or gaseous mixture that has the same proportions of its components
pure substances- substances that are made of only one type of atom or molecule
density and hardness
hardness
boiling point
melting point-
compounds- omposed of atoms from more than one element held together by chemical bonds.
molecules- Molecules are made up of atoms that are held together by chemical bonds
isotopes- atoms that have the same number of protons but different amount of neutrons
Nanotechnology- is a branch of materials science that investigates the design, properties and applications of materials produced on this scale.
nano-materials are substances, both natural and synthetic that are composed of single units that exist in nanoscale
carbon nanotube-
periodic trends-
atomic radius - atomic radius of a chemical element is a measure of the size of its atoms, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding cloud of electrons
across period- decrease due to increase of protons in necules
down group- increase due to another electron shell level
electronegativity-is the power of an atom in a molecule to attract the shared pair of electrons.
across period- increase due because stronger attraction
down group- less attraction due to increase electron level so necules has less effect
ionisation energy- ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms from its valence shell.
across period- increase due to increase of proton in necules of the atom
down group- decrease due to increase of electrom level
bonding
covalent- A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms.
softness-
relatively low melting point and boiling points- have weak forces of attraction between the binding molecules.Thus less energy is required to break the force of bonding.
non-electrical conductivity- because all electrons are being used
metallic bonding- Metallic bonding is a type of chemical bonding that rises from the electrostatic attractive force between conduction electrons and positively charged metal ions de-localised
electrical and thermal conductive- due to the delocalise electron that are able to free flow and carry energy and charge
mailability and ductile- This is because of the ability of the atoms to roll over each other into new positions without breaking the metallic bond.
melting and boiling point- The attraction between the metal ions and the delocalised electrons must be overcome to melt or to boil a metal. These attractive forces are strong, so metals have high melting and boiling points
hardness- the strength of a metallic bond depends upon: The greater the number of valence electrons for delocalisation the stronger is the metallic bond.
ionic- Ionic bonding is the complete transfer of valence electron(s) between atoms between metal and a non-metal
digram- see word
electrical conductivity during molten state- charged electrons are able to freely move then molten
high melting and boiling point- ionic bonds are very strong - a lot of energy is needed to break them.
brittleness- strong force bonding force
hardness- strong bonding force
covalent network bonding- solid is a chemical compound (or element) in which the atoms are bonded by covalent bonds in a continuous network extending throughout the material.
no-electical conductivity
brittleness
high melting and boiling point