Bonding Flashcards
give the definition of metallic bonding
its the strong electrostatic attraction between positive metal ions and sea of delocalised electrons
how do you draw metallic bonding diagrams
always draw 6 atoms, work out charge of ion and draw correct number of electrons (sum of all charges)
how do you compare the strength of metallic bonds
Ions have stronger metallic bonding if;
- they have higher charge
- if they are the smaller metal ion
- if they have more delocalised electrons
Finally state that there’s a stronger electrostatic attraction between positive metal ions and delocalised electrons
why is the bonding in magnesium stronger than in sodium
Mg2+ has higher charge than Na+
Mg2+ is a smaller ion than Na+
Mg2+ has more delocalised electrons than Na+
Therefore Mg2+ has stronger electrostatic attractions between positive metal ions and delocalised electrons
Give the properties of metals
-Good electrical and thermal conductors
-They are strong
-They are malleable and ductile
-Have high melting/boiling points
How are metals good conductors of heat and electricity
- they are good conductors of heat because delocalised electrons help transfer energy through the metal very efficiently
-the electrons are delocalised as they can flow and carry charge so can conduct electricity
How are metals strong and why do they have high Mp and Bp’s
- they have strong electrostatic attractions between positive metal ion and delocalised electrons so stronger the strength of metallic bond, the higher the Mp and Bp
what is the definition for covalent bonding
shared pair of electrons between 2 atoms
the shared electrons hold together because the attraction forces are stronger than repulsion forces
what are macromolecular structures
carbon, silicon and silicon dioxide
why do macromolecular structures have high Mp and Bps
because they have many strong covalent bonds which require lots of energy to be broken
what are allotropes
they are different structural forms of the same element
what are the properties of diamond
-each carbon makes 4 covalent bonds so its got a high Mp and Bp because lots of the covalent bonds need lots of energy to be broken
-doesn’t conduct electricity as it has no free/delocalised electrons
what are the properties of graphite
-each carbon akes 3 covalent bonds and one outer electron becomes delocalised so graphite can conduct electricity as delocalised electrons can move
-layers of carbon which makes it soft
-between layers are weak intermolecular forces
what are simple molecular structures made up of
molecules
what are the properties of a simple molecular structure
- has strong covalent bonds between atoms and weak intermolecular forces between molecules
- have low melting and boiling points because intermolecular forces are weak so require little energy to be broken
- don’t conduct electricity because there’s no delocalised electrons
what is the structure for ionic bonding
giant ionic lattice
definition of ionic bonding
an ionic bond is the strong electrostatic attractions between oppositely charged ions (metals and non-metals)
give the properties of ionic compounds
- high boiling and melting points because they have strong electrostatic attractions which need lots of energy to break them
- they can conduct electricity when molten or aqueous as ions are free to move and carry current
-ionic compounds tend to be brittle and shatter easily
formula for ammonium ion
NH4+
formula for hydroxide ion
OH-
formula for nitrate ion
NO3-
formula for nitrite ion
NO2-
formula for hydrogencarbonate ion
HCO3-
formula for chlorate (I) ion
ClO-
formula for chlorate (v) ion
ClO3-
formula for carbonate ion
CO3 2-
formula for sulfate ion
SO4 2-
formula for sulfite ion
So3 2-
formula for dichromate ion
Cr2O7 2-
phosphate ion formula
PO4 3-
what is a coordinate bond and what are the conditions to create one
- a shared pair of electrons between 2 atoms when both electrons come from same atom
- for this you need one atom with lone pair of electrons and one atom with space for 2e- so it can accept them
explain the formation of the coordinate bond in NH4+
The lone pair of electrons on N from NH3 is donated to the H+
what does valence mean
the outer shell of electrons ( the electrons used in bonding)
what is the strength of repulsion of electrons
bondpair- bondpair repulsion is less than bondpair - lonepair repulsion which is less that lonepair- lonepair repulsion
what is electronegativity
the power of an atom to attract the pair of electrons in a covalent bond
which factors determine how electronegative an element is
- nuclear charge
- size of atom
- shielding
why does the electronegativity increase across a period
increases because
- they all have same number of shells so similar shielding
- so numbers of protons increase
- atomic radius increases so
- there’s a strong attraction between nucleus and pair of electrons in a covalent
why does C - H not have a partial charge
because it has too similar electronegativity
what does a non - polar molecule consist of
- atoms bonded have same electronegativity
- symmetrical distribution of electrons / charge
- dipoles cancel out
(eg. Cl-Cl)
what does a polar molecule consist of
- differences in electronegativity is shown by a partial charge
- delta - is given to the more electronegative atom
- delta + is given to the less electronegative atom
- unsymmetrical distribution of electrons leads to a polar molecule
(eg. H-Cl)
how do you determine is a molecule has hydrogen bonding
- if it has a lone pair and the following bonds
O - H
N - H
F - H
how do you determine if a molecule has permanent dipole - dipoles
it will be a polar molecule (unsymmetrical)
how do you determine if a molecule has induced dipole dipoles ONLY
it will be a non- polar molecule (symmetrical)
how does hydrogen bonding arise
- large difference in electronegativity between O , N , F when bonded to H
- H therefore gets a very strong delta + charge
- lone pair of electrons on another molecule is attracted to delta + H.
how do you draw Hydrogen bonding in water
straight line between O - H - lone pair - O - H
how does permanent dipole - dipole forces arise
- in polar molecules
- permanent partial charges ( delta + , -) cause a dipole across the molecule
- delta + on one molecule is attracted to delta -on another molecule
how does a Van der Waals forces arise
- present in all molecules, but is only force in non-polar molecules
- random movement of electrons creates an uneven distribution of electrons and creates a temporary dipole dipole
- this will then induce a dipole on neighbouring molecules
- dipoles attract
what affects the strength of a van der vaals force
- size of molecule , larger the molecule stronger the van der vaals force
- molecular mass (Mr) higher the Mr stronger the VDW force
- surface are contact between carbon chains, longer the carbon chain the stronger the VDW force
describe hydrogen bonding in ice, proteins and DNA
- ice is less dense than water because the hydrogen bonds in ice hold the molecules further apart so there’s more gaps and spaces between molecules
- proteins are held in 3D complex sha[es by hydrogen bonds between N-H groups and C=0 groups
- hydrogen bonding between DNA bases A-T C-G
why does argon have the lowest mp
its a single atom that’s difficult to polarise
