BONDING Flashcards
define ionic bonding
electrostatic forces of attraction between oppositely charged ions are formed by electron transfer in a lattice, the metal ion will lose an electron to gain positive charge, the metal atom will gain an electron to get a negative charge.
define covalent bonding
a single covalent meaning the electron pairs are shared and multiple bonds contain multiple pairs of electron, the dative covalent shares a pair of electrons per atom and the size of ions
define metallic bonding
attraction between delocalised electrons and positive ions are arranged in a lattice, the strength of bonding will be affected by the strength of nuclear attraction, number of delocalised electrons per atoms and size of the ions
Describe the repulsion between the charge clouds
bonding pair and lone pair of electrons as charge clouds repel each other, electron pair in the outer shell of the atoms will arrange themselves as far as possible to minimise the repulsion.
lone pair- lone pair> lone pair- bonding pair> bonding pair- bonding pair.
how much does repulsion decrease by
about 2.5 degrees
define electronegativity
power of an atom to attract a pair of electrons in a covalent bond
define trend in electronegativity across a period
it increases across a period, protons increase and atomic radius decreases because electrons are in the same shell are pulled in more, it will decrease down a group the distance between the nucleus and outer electron will increases and shielding of the inner electron will also increase
define covalent bond polarity
compounds with elements of similar electronegativity and small differences
define ionic bond polarity
compound with elements of different electronegativity and large difference
define permanent dipole
elements in a bond have different electronegativity, when a bond in polar covalent has unequal distribution of electron and produces charge separation
when does permeant dipole occur
it occurs between polar molecules, high melting points and boiling points, they contain permanent dipole, they are asymmetrical and contain bonds where there is significant decrease in electronegativity.
when does van Der wall forces occur
they occur in all molecular substances because electrons are moving randomly so electron density can fluctuate and parts of the molecule will become more/less negative. these instantaneous dipoles will form dipoles with neighbouring molecules.
what factors can affect a dipole from forming
more electrons are in the molecule so there is a higher chance of forming temporary dipole making forces stronger so there is a higher boiling point.
why does boiling point increase across a group
it increases the number of electrons in bigger molecules causing an increase in van Der wall size due to large surface area between molecules so more formation
when does hydrogen bonding occur
occurs in molecules that have H attached either on N,O,F with available lone pairs- large electronegativity difference.
