bonding, structure and properties
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Describe the properties of a covalent molecular substance
Low Mp and Bp Soluble in a non-aqueous solvents (white spirit) Never conductive Made of molecules (neutral) Liquid or gas at room temp (weak intermolecular forces)
what are the 4 shapes of molecules
linear, angular, trigonal pyramidal and tetrahedral
what is a molecule
a group of atoms held together by covalent bonds
what is a covalent bond
bond between two non metals strong bond formed between atoms as a result of electrostatic attraction between the positive nuclei and the pairs of negative elections which are shared only the outer electrons are involved in bonding
what and why are noble gases
group 8 of the periotic table they are unreactive element due to their full outer shell of electrons
what are the rules of electron shells/ energy levels
the first level can only have 2 electron, the others can have up to 8 - only draw the outer shell when drawing the bonds between atoms
why do atoms form bonds
to gain or loose outer electrons to get a full outer shell - to reach the same stable outer electron arrangement as a noble gas
what is a valency
the valency is the number of bonds an atom can make
what are the 2 possible structures for a covalent substance
covalent networks or covalent molecular substances
explain what a covalent network is
when all atoms in the substance are connected together by covalent bonds e.g. diamond & graphite due the strong covalent bonds
explain what a covalent molecular substance is
covalent molecules are atoms connected by covalent bonds. The molecules are separate to each other and held together by (usually weak) intermolecular bonds/forces strong bonds within the molecule
what do the terms aqueous, solvent and solute mean
aqueous = dissolvible in water solvent = dissolver solute = dissolved
what is the solubility of covalent compounds like ?
most covalent compounds dissolve in non-aqueous solvents
what is electricity
electricity is the flow of charged particles (electrons) around a circuit from negative - to positive =
what is the conductivity of covalent substances
most covalent substances don’t conduct (graphite does)
what charge will a metal ion have
positive charge (loses electrons)
what charge will a non-metal ion have
negative (gains electrons)
what is an ionic compound / what is an ionic bond
ionic compounds contain both metal (positively charged) and non-metal (negatively charged ions) Ionic bonding is the electrostatic attraction between the positive (metal) and negative (non-metal) ions
what structure is a ionic compound arranged in?
a lattice (non-metal/negative ions are bigger, metal/positive ions are smaller)
what does variable valency mean ? and what group does the term apply to?
the transition metals (group 2) - the amount of outer electrons can vary
what state and why are ionic compounds at room temperature
solid because lots of energy is required to break the strong ionic bonds (electrostatic forces/attraction) between the positively and negatively charged ions.
describe the solubility of ionic compounds or salts
when ionic compounds or salts dissolve in water the ionic lattice breaks up to give ions that are free to move and are surrounded by water molecule these compounds dissolve in water to give an aqueous solution
describe the conductivity of ionic compounds
ionic compounds conduct electricity when in an aqueous solution, they also conduct when melted (liquid) They can conduct when molten or as a solution as the ions (charged particles) are free to move
What is electrolysis?
the process of passing electricity through an ionic melt/solution to split the elements - used in chemical industry for extracting an purifying metals from their ores the solution/melt is called the electrolyte