L4-covalent and non-covalent bonding

why do bonds form

as atoms want a full outer shell of electrons they will either try to lose the electrons ( ionisations ) or share and gain electrons /form bonds

what is a bond ?

a bond is a force that holds atoms together in a molecules/compound and they form due to the transfer or sharing of electrons

what is ionisation

ionisation is when ions are formed when atoms lose or gain electrons in an ionic bond to become charged particles

explain how ionic bonding works

it occurs between a metal and a non-metal the metal becomes a positive ion and loses an electron whilst the non-metal gains electrons to become negative ions the salts formed are held together by strong electrostatic forces

what is a covalent bond and why does it occur

a chemical bond that involves the sharing of pairs of electrons between atoms

it happens as when the two atoms are brought closer together the orbitals now overlap and merge into a single bond orbital that contains both electrons

explain sigma bonds

they are the strongest type of covalent bond and they form when orbitals overlap in a head-on-head arrangement

they can form when 2 s-orbitals merge

also can be formed when an s and a p orbital overlap

also when a sp and an s orbital overlap

Explain pi bonds

pi bonds are covalent bonds formed from the overlap of two orbital lobes on one atom with two orbital lobes on another side to side ( two p orbitals over lapping )

area of high electron density

what is a hydrogen bonding

its a partially electrostatic attraction between a hydrogen ( which is delta positive ) and the electronegative N,O,F

its an electrostatic dipole-dipole interaction

What are Van der Waals forces?

weak forces that attract neutral molecules to one another found in gases and in almost all organic liquids and solids

they can occur in three different ways

1.neutral molecules can have permanent dipoles e.g. water

2.induced dipoles - molecules with a permanent dipole may temporarily distort the electric charge in a nearby molecule

3. dispersion forces-molecules with no permanent dipoles can form temporary dipoles can form randomly as electrons are always moving sometimes on one side more than the other

what is pi stacking

attractive non covalent bonds between aromatic rings ( which contain pi bonds )

the three arrangements are sandwich, t-shaped and parallel displaced

explain hydrophobic interactions

theses interactions are the segregation between water and non-polar substances e.g. water and oil not mixing

water contains a strong network of hydrogen bonds but non-polar molecules like hydrocarbon chains for example cant form h- bonds

explain how amphiphilic molecules ( mainly proteins ) react in water

they will form micelles in water, the hydrophilic head unit is found on the outside and the hydrophobic tails on the inside

when the protein folds into a three dimensional shape, its common to have a hydrophobic core composed with hydrophobic elements

explain protein structure ( primary, secondary, tertiary )

primary- sequence of amino acids in a polypeptide held together by peptide bonds

secondary-the additional folding into either beta-pleated sheets or alpha helix's through hydrogen bonding interactions

tertiary-the three dimensional shape of a protein molecule, the secondary structure is folded into a compact globular structure driven by hydrophobic interactions, salt bridges and hydrogen bonds and van der Waals

quaternary-assemblies of two or more polypeptide chains into one functional unit