BONDING Flashcards
Define ionic bonding:
Ionic bonding is the electrostatic force of attraction between oppositely charged ions formed by electron transfer.
what happens to metals and non metals in ionic bonding?
Metal atoms lose electrons to form +ve ions.
Non-metal atoms gain electrons to form -ve ions.
What is the structure of ionic crystals?
Ionic crystals have the structure of giant lattices of ions
What makes ionic bonds stronger and melting points higher?
Ionic bonding is stronger and the melting points higher when the ions
are smaller and/ or have higher charges.
E.g. MgO has a higher
melting point than NaCl as the ions involved (Mg2+ & O2- are smaller and have higher charges than those in NaCl , Na+ & Cl- )
What is the ionic radii of positive ions?
Positive ions are smaller compared to their atoms because it has one less shell of electrons and the
ratio of protons to electrons has increased so there is greater net force on remaining electrons
holding them more closely.
what is the ionic radii of negative ions?
The negative ion has more electrons than the corresponding atom but the same number of protons. So the pull
of the nucleus is shared over more electrons and the attraction per electron is less, making the ion bigger.
what are the trends in ionic radii down a group?
Within a group the size of the ionic radii increases going down the group. This is because as one goes down the group the ions have more shells of electrons.
what is a covalent bond?
A covalent bond is a shared pair of electrons
what is a dative covalent bond ?
*aka co-ordinate bonding
A dative covalent bond forms when the shared pair of electrons in the covalent bond come from only one of the bonding atoms
Define metallic bonding:
Metallic bonding is the electrostatic force of attraction between the
positive metal ions and the delocalised electrons
List 3 factors that effect the strength of metallic bonding:
- Number of protons/ Strength of nuclear attraction. The more protons the stronger the bond
- Number of delocalised electrons per atom (the outer shell electrons are delocalised). The more delocalised electrons the stronger the bond
- Size of ion.The smaller the ion, the stronger the bond.
what is the structure of a simple molecule and list examples?
*mostly liquids and gases
*it has intermolecular forces (van der
Waals, permanent dipoles, hydrogen
bonds) between molecules
*Iodine , Ice ,Carbon dioxide,Water,Methane
What is the structure of a macro-molecule and list examples?
- solids
- its a giant molecular structure
- Diamond,Graphite,Silicon dioxide,Silicon
What is the structure of metals in metallic bonding?
*list features
- Giant metallic lattice
- shiny metals
- malleable as the positive ions in the lattice are all identical.so the planes of ions can slide over one another
Whats the bp & mp in ionic bonding?
high- because of giant lattice of ions with strong electrostatic forces between oppositely charged ions
What is the mp&bp of a simple molecular structure?
low- because of weak intermolecular forces between
molecules (specify type e.g van der waals/hydrogen
bond)
what is the mp&bp of a macromolecular structure?
high- because of many strong covalent bonds in
macromolecular structure. Take a lot of energy to break the many strong bonds.
what is the mp&bp in metallic bonding?
high- strong electrostatic forces between positive ions and sea of delocalised electrons
are ionic compounds,metals, macromolecular substances and simple molecular substance soluble in water?
*state if each of these are soluble in water
ionic compounds-generally good
simple molecular substances-generally poor
macromolecular substances-insoluble
metal-insoluble
whats the conductivity of ionic compounds when solid and molten?
solid: poor-ions cant move as its fixed in a lattice
molten: good-ions can move
what is the conductivity of simple molecular substance when solid and molten?
solid: poor-no ions to conduct and electrons are localised
molten: poor-no ions
what is the conductivity of macromolecular substances when solid and molten?
solid:diamond-poor as electrons can’t move(localised)
graphite-good as free delocalised electrons
between layers
molten:poor
whats the conductivity of metals when solid and molten?
solid: good-delocalised electrons can move throughout structure
molten: good
Whats the structure of ionic compounds and list examples?
- crystalline solids
- giant ionic lattices
- sodium chloride,magnesium oxide
What is electronegativity?
The power of an atom to attract the pair of electrons in a covalent bond to itself.
What elements are the most electronegative and state their values?
F- 4.0
O-3.5
N-3.0
Cl-3.0
trends in electronrgativity down a group?
It decreases down a group because the distance between the nucleus and the outer electrons increases and
the shielding of inner shell electrons increases
trends in electronegativity across a period?
Electronegativity increases across a period as the number of protons increases and the atomic radius
decreases because the electrons in the same shell are pulled in more
explain how elecronegativity can determine whether a compound is ionic or covalent?
A compound containing elements of similar electronegativity and hence a small electronegativity difference will be purely covalent
A compound containing elements of very different electronegativity and hence a very large electronegativity difference (> 1.7) will be ionic
when does a polar covalent bond form?
A polar covalent bond forms when the elements in the bond have different
electronegativities . (Of around 0.3 to 1.7)
what is a polar covalent bond?
a polar covalent bond has an unequal distribution of electrons in the bond and its produces a dipole(delta+ &delta- end)
are symmetrical molecules polar molecules?
A symmetric molecule will not be polar even if individual bonds within the
molecular are polar.
Symmetric molecules
The individual dipoles on the bonds ‘cancel out’ due to the symmetrical shape of the molecule.
There is no net dipole moment: the molecule is
non-polar
What are van der waals forces?
*aka transient forces,induced dipole-dipole forces
- These are intermolecular forces that occur between all molecular substances and noble gases.
- any molecule that electrons are moving constantly and randomly one part of the molecule can become more negative or less negative creating a small transient or temporary dipole.
- these small dipoles can then cause dipoles to form in neighboring molecules and this is called induced dipoles.
explain factors that effect size of van der waals
The more electrons there are in the molecule the higher the chance that temporary dipoles will form. This makes the Van der Waals stronger between the molecules and so boiling points will be greater.
what are permenent dipole dipole forces and where do they occur?
•Permanent dipole-dipole forces occurs between polar molecules
•It is stronger than Van der Waals and so the compounds have higher boiling points
•Polar molecules have a permanent dipole.
•Polar molecules are asymmetrical and have a bond where there is a significant difference in
electronegativity between the atoms.
Where do hydrogen bonds occur?
It occurs in compounds that have a hydrogen atom attached to one of the three most electronegative atoms of nitrogen, oxygen and fluorine, which must have an available lone pair of electrons
list the order of strongest intermolecular force to the weakest:
vdw-weakest
permenant dipole-dipole force
hydrogen bonding-strongest
Shapes of molecules 1
ans
shapes of molecules 2
ans
shapes of molecules 3
ans
shapes of molecules 4
ans
shapes of molecules 5
ans
shapes of molecules 6
ans
shapes of molecules 7
ans
