bonding, structure and properties Flashcards
what is a compound
a compound is a substance which 2 or more elements are chemically combined
what are the three types of chemical bonds
ionic - bonding in ionic compounds
metalic - bonding in metals
covalent - bonding in giant covalent structures
what are the properties of ionic compounds
strong electrostatic attraction between oppositely charged ions means ionic compounds have HIGH MELTING AND BOILING POINTS
in a solid state, ionic compounds do not conduct electricity as ions are fixed in place
when ionic compounds are molten / dissolved, ions can move around so then ionic compounds conduct electricity
they are BRITTLE
what are the properties of metallic compounds
the layers pf ions in metallic compounds are able to slide over each other, so metals are malleable and ductile
the delocalised electrons can move through the metal and carry charge, so metals conduct electricity and heat
metallic bonds are very strong and require large amounts of energy to be broken, giving most metals high melting and boiling points
what are the properties of simple molecular covalent substances
simple molecules (e.g. oxygen) have week intermolecular forces between molecules, so they have low melting and boiling points
simple molecular covalent substances do not conduct electricity because simple molecules do not have an overall charge
they are usually gas or liquids
what are the properties of giant covalent substances
substances with a giant covalent structure are solids with very high melting points
explain the bonding and structure in metallic compounds
The electrons in the outer shell metal atoms are delocalised and so they are free to move through the whole structure – sea of delocalised electrons
Metallic bonds formed due to the electrostatic attraction between the positively charged metal ions and the negatively charged delocalised electrons
how does ionic bonding take place
Electrons in the outer shell of the metal are transferred
Metal atoms lose electrons to become positively charged ions
Nonmetal atoms gain electrons to become negatively charged ions
The electrostatic attraction family obviously charge ions form is a giant ionic lattice
The electron transfer can be represented by dot and cross diagram
how are covalent bonds formed
When atoms share pairs of electrons, they form covalent bonds
the bond between these atoms are strong
dot and cross diagrams can be drawn to represent the sharing of electrons
why do simple molecular substances have low melting and boiling points
Weak intermolecular forces between molecules – these are broken in melting or boiling, not a strong covalent bonds
The intermolecular forces increase with the size of the molecules, larger and molecules have high melting and boiling points
what are the properties of diamond?
its bonding and structure
It is very hard, had a very high melting point and does not conduct electricity
Each carbon is joined to 4 other carbons covalently - covalent bonds need a lot of energy to be broken which results in very high melting points
This is the maximum number of bonds each carbon atom can make
what are the properties of graphite
its bonding and structure
Each carbon is covalently bonded to 3 other carbons, forming layers of hexagonal rings which have no covalent bonds between the layers
The layers can slide over each other due to the absence of covalent bonds between the layers, but they are weak intermolecular forces between the layers – so graphite is soft and slippery
One electron from each carbon atom is delocalised so it can conduct electricity
what are the properties of graphene
its bonding and structure
Its structure resembles a single layer of graphene
graphene has a very high melting point due to the very strong covalent bonds between the carbon atoms that require large amounts of energy to be broken
Conducts electricity due to the delocalised electrons that are free to move through its structure
what are fullerenes
Molecules of carbon with hollow shapes
They are based on hexagonal rings of carbon atoms, but they may also contain rings with five or seven carbon atoms
what are carbon nanotubes
cylindrical fullerenes with very high length to diameter ratios
the have very high tensile strength and conduct electricity due to the delocalised electrons present
