notes Flashcards
what is the definition of ionic bonding?
strong electrostatic attraction between oppositely charged ions
state and explain the trend in atomic radii & electrostatic attraction in group 1.
- atomic radii increases down the group & larger sized atom down the group
- more complete electron shells
- more distance from nucleus
- more shielding from nucleus to outer electron
- weaker electrostatic attraction
which 2 factors affect the strength of ionic bonding?
- ionic radii
- charge of ion
in which way does radius & charge of atom leads to a stronger bond?
- smaller radius & higher charge
what is the trend atomic radii in a group and a period?
- increases down a group and decreases through a period
why does Mg2+ have a stronger charge than Na+?
- higher charge
- attracting the same number of electrons
- therefore electrons are attracted more strongly & closer to nucleus
how are cations formed and what charge do they have?
loses electrons, positive
how are anions formed and what charge do they have?
gains electrons, negative
why does ionic compounds have high melting temperatures?
large amount of energy needed to overcome electrostatic attraction in lattice
why are ionic compounds brittle?
layers of ions slide over and repel ions of the same charge
describe the electrical conductivity of ionic compounds.
does not conduct in solids but yes when molten
- no delocalised e- free to move in solids but ions are mobile in molten
describe the solubility of ionic compounds.
only soluble in water & polar solvents, as energy needed to break is supplied by hydration of ions
what is a covalent bond?
strong electrostatic attraction between 2 nuclei and the shared pair(s) of electrons between them
what is a sigma bond?
single covalent
what is a pi bond?
double / triple covalent bond
which bond forms first, sigma / pi?
sigma
explain the definition of bond length.
distance between nuclei of 2 covalently bonded atoms
explain the definition of bond strength.
energy needed to break 1 mole of the bond in gaseous state
explain the relationship between bond length & bond strength.
bond length decreases as bond strength increases
- higher electrostatic attraction between 2 nuclei & shared pair of e- in overlapping orbitals
define electronegativity.
ability of an atom to attract a bonding pair of e- in a covalent bond
what’s a dative covalent bond?
a covalent bond where an atom donates a lone pair
what causes the shape of the ion?
e- pairs arrange themselves around the central atom to get minimum repulsion
2 bond pairs, 0 lone pairs
name the shape & angle.
linear, 180
3 bond pairs, 0 lone pairs
name the shape & angle.
trigonal planar, 120
4 bond pairs, 0 lone pairs
name the shape & angle.
tetrahedral, 109.5
5 bond pairs, 0 lone pairs
name the shape & angle.
trigonal bipyramidal, 90 & 120
6 bond pairs, 0 lone pairs
name the shape & angle.
octahedral, 90
2 bond pairs, 2 lone pairs
name the shape & angle.
bent / v-shaped, 104.5
3 bond pairs, 1 lone pair
name the shape & angle.
trigonal pyramidal, 107
should there be a small or large electronegativity difference for the bond to be covalent?
small (<1.7)
where does london forces occur in?
all molecules
are bigger molecules more likely to induce temporary dipoles? why?
yes
more electrons -> stronger london forces
what intermolecular force forms when there is a polar molecule?
permanent dipole-dipole
which specific bonds usually display dipole-dipole forces?
C-Cl, C-F, C-Br, H-Cl, C=O
to which 3 atoms does hydrogen bonding occur?
N, O, F (3 most electronegative)
what is the bond angle around the H atom at a hydrogen bond?
180
why do unbranched alkanes have a higher boiling temperature than branched alkanes?
more points of contact between adjacent molecules -> more london forces
how could it be determined if a compound is soluble in water?
if they could form hydrogen bonds with water molecules
how could it be determined if compounds could dissolve in a solvent or not?
they would have similar intermolecular forces
what is the definition of metallic bonding?
electrostatic force of attraction between positive metal ions & delocalised e-
which 3 factors increases the strength of metallic bonding?
- higher number of protons
- more delocalised e-
- smaller ion
4 bond pairs, 2 lone pairs
name the shape & angle.
square planar, 90