2.2 covalent model part 2

difference in electronegativity of the bonded atoms

bond polarity and molecular geometry

relative measure of how an atom attracts a pair of electrons in a covalent bond

the electron pair is equally attracted to their positive nucleii, bond will be symetrical, even distribution of negative charge

pair of electrons is more strongly attracted to more electronegative atom, bond is polar, meaning there is an unequal distribution of charge between two atoms, there is a partial negative charge on more elctronegative atom, and partial positive to the less electronegative atom

the difference in electronegativity between the two atoms in the covalent bond

increases up periodic table and increases from left to right

next to each other probably not polar, seperation of 1 element then bond is polar, seperation of 2 or 3 elements then bond will be strong polar, seperation of 4 likely not covalent bond

polar bond

ionic bond

for molecule to be polar its shape must be such that the centres of positive and negative cannot by symmetrical arranged, if charges are symmetrical over whole molecule they can cancel each other out, resulting in the molecule itself being non-polar.

a dipole

using an arrow poiting towards the region of negative charge

forces resulting from strong bonds within the molecule or structure, both giant and simple covalent molecular have these to break these bonds often recquire high energy input

the force of attraction between neighbouring molecules or atoms are weak

london dispersion forces dipole dipole forces hydrogen bonding from wekest->strongest

present in all atoms or molecules that have electrons the movement of electrons in the orbitals of atoms or molecules gives rise to temporary dipole, when this is formed it can induce the formation of a dipole in neighbouring atoms or molecules electrostatic attraction between the temporary and induced dipoles results in a weak attractive force to arise= london force

combnation of both london and dipole dipole forces

• in an atom or molecule movement of electrons results in the formation of a spontaneous temporary dipole 2.close proximity to another moelcule induces a dipole to form in the other molecule the elctron cloud becomes distorted and the molecule is polarized 3.temporary and induced dipoles attract each other forming a weak temporaray london force

happens more frequently in lower temperatures as atoms or molecules move more slowly increasing frequency of force formation

in non polar molecules london forces may be the only attractive force between molecules. Since the force is the weakest of the intermoleculcular forces, non polar molecules are often gases or liquids and slids with relitevly low melting points

1.increasing number of electrons 2.increasing the volume of the electron cloud 3.increasing the contact area between molecules

the greater the molar mass the bigger the number of electrons and the weaker will be the attraction for the electrons for the nucleus and the ease with which the electron cloud can be polarized (induced dipole)

the greater the volume of the electron cloud the weaker will be the attraction of an electron for the nucleus and the ease with which the electron cloud can be polarised (induced dipole)