bonding Flashcards
What is ionic bonding
the electrostatic attraction between positive ions and negative ions.
it holds together cations (positive ions) and anions (negative electrons) in an ionic compound
what is the definition of covalent bonds
attraction between a shared pair of electrons and the nuclei of the bonded atoms
how many covalent bonds does each element usually form
Hydrogen- 1 bond
Oxygen- 2 bonds
Nitrogen-3 bonds
Carbon- 4 bonds
how to draw complicated covalent dot and cross
take it slow
eg for SF6
draw the s out first
you know it has 6 electrons in the outer shell
but because we need to bond 6 fluorine atoms to it we would need all these electrons to be unpaired so each can bond to each of fluorine’s one unpaired electron
just think and add each fluorine atom at a time until you have added all 6 fluorine’s
multiple covalent bonding
double covalent bonds- the electrostatic attraction is between two pairs of shared electrons (in the middle) and the nuclei of the bonded atoms
eg C=C and C=O are very important
triple covalent bonds= electrostatic attraction is between 3 shared pairs of electrons and the nuclei of the bonded atoms. ( three shared pair of electrons in the middle)
for both a double and triple bond all the atoms want 8 electrons in their outer shell so the electrons left on each atom that is not involved in the double or triple bond should add with those in the middle to 8
what is a dative covalent bond
a covalent bond which the shared pair of electrons has come from the same atom (the other atoms has contributed no electrons to the bond and just slots on)
the shared pair of electrons has to have originally been a lone pair on the atom
what does a lone pair of electrons mean
a pair of electrons that are on the outer shell and not involved in any bonding
what does average bond enthalpy mean
a measurement of the covalent bond strength
How to draw dot and cross for any covalent
- find total number of valence (outer) electrons
- put element that is least electronegative first (Hydrogen always goes around the outside)
- draw out all the atoms and put the bonds in-between atoms
- complete the octet for outer atoms first then the complete the octet of the central atoms
- if central atoms does not have an octet then move electrons from outer electrons to form double or triple bonds for the central atom.
remember to not go over number of valence electrons
link between melting point and ionic charge
when ionic charge increases melting point increases
metallic bonding and structure
in a solid metal structure each atom has donated its outer electrons to a shared pool of electrons, which are delocalised (able to move) throughout the structure
positive metal ions (cations) are left behind
metallic bonds formed between delocalised electrons and cations
the cations are in a fixed position, maintaining the structure and shape of the metal
the delocalised electrons are mobile and are able to move throughout the structure (which is why metals can conduct)
what can carry charge
mobile charge carriers (electrons, ions)
giant covalent properties
structure and bonding dominated by their covalent bonds.
high melting and boiling point (as strong covalent bonds)
not soluble as covalent bonds are too strong to be broken by interactions with solvent
non-conductors as all electrons are involved in covalent bonding- except for graphite and graphene as they have one electron each available for conducting electricity
what happens when things are solluble and dissolve
the particles of the solvent break down the stricture of whatever they are dissolving
