3.1.3 Bonding

what forces do all simple covalent molecules have

intermolecular

what 3 types of intermolecular forces are there

van Der walls, dipole-dipole, hydrogen

what is the weakest intermolecular force

van der walls

what forms a van der walls force

an instantaneous dipole due to electron distribution

why does electron distribution induce dipole

electrons repel

what can increase strength of van der walls

more electrons

what molecules have van der walls

all molecules

what forms a dipole-dipole force

permanent attraction between molecules due to electronegativity and bond polarity

what must the element be to have dipole-dipole

asymmetrical

why do symmetrical molecules not have dipole-dipole

polar bonds cancel out

what is the strongest type of inter molecular forces

hydrogen bonds

how strong are intermolecular forces

weak

what elements must be present for a hydrogen bond

hydrogen and fluorine, oxygen or nitrogen

what are hydrogen bonds

direct bonds with hydrogen and a highly electronegative element

does a lone pair affect hydrogen bonding

no

what angle must hydrogen bonds be drawn at

180 degrees

what is melting point affected by

strength of intermolecular bonds

define electronegativity

the ability of an atom to attract electrons in a covalent bond towards itself

which element has the highest electronegativity

Fluorine

which element is the least electronegative

Caesium

Name 3 factors which affect electronegativity

nuclear charge, atomic radius, shielding

define sheilding

the shells between the nucleus and outer electron

define non-polar

no difference between two elements in electronegativity

define polar

difference between two elements in electronegativity

what does delta positivity represent

the less electronegative element

what does delta negative represent

the more electronegative element

what can a difference in electronegativities induce

permanent dipole

what is the relationship between bonding and lone pairs

repulsion

what repulsion is stronger, lone-lone or bonding-bonding

lone-lone

shape: 2 bonding pairs

linear

linear bond angle

180

shape: 3 bonding

trigonal planar

trigonal planar bonds angle

120

shape: 4 bonding

tetrahedral

tetrahedral bonds angle

109.5

shape: 3 bonding, 1 lone

pyramidal

pyramidal bond angle

107

shape: 2 bonding, 2 lone

V or bent shape

V or bent shape bond angles

104.5

shape: 5 bonding

trigonal bypyramidal

trigonal by pyramidal bond angles

120 & 90

shape: 4 bonding, 1 lone

modified trigonal bypyramidal

modified trigonal bypyramidal bond angles

118 & 89

shape: 3 bonding, 2 lone

T shaped

T shaped bond angle

86

shape: 2 bonding, 3 lone

linear

linear (2bp, 3lp) bond angle

180

shape: 6 bonding

octahedral

octahedral bond angle

90

shape: 4 bonding, 2 lone

square planar

square planar bond angle

90

name the four types of crystal structures

ionic, metallic, macromolecular, simple molecular

what is a macromolecular structure

a giant covalent molecule

give 4 examples of physical properties

boiling point, melting point, solubility and conductivity

what mp and bp do ionic crystals have

high

why do ionic crystals have high mp and bp

electrostatic forces are strong and require a lot of energy to break

when can ionic crystals conduct

when molten or in a solution

why can ionic crystals conduct when molten

the ions are free to move and carry charge

are ionic crystals brittle

yes

why are ionic substances brittle

layers of ions repel breaking the lattice

why do atoms with more ions have a greater mp in ionic crystals

there are more electrostatic forces

can metals conduct

yes

why do metals conduct

the sea of electrons is free to move and carry charge

why are metals malleable

layers of positive ions are able to slide over each other

what state are metals normally at rtp

solid

what kind of melting point do metals have

high

why do higher charged ions have higher ups in metals

more protons means more electrons so stronger electrostatic forces

what forces hold simple molecules together

van der walls

are van Der walls in simple covalent molecules weak or strong

weak

what boiling/melting points does simple covalent molecules have

low

can simple molecules conduct

no

why can’t simple molecules conduct

there are no charged particles

what bonding does a macromolecule have

covalent

why do macromolecules have a high melting point

they have multiple strong covalent bonds

what structure has low melting points

simple molecular

what structure is diamond

macromolecular

how many covalent carbon-carbon bonds does diamond have

4

why is diamond so strong

it has 4 covalent carbon-carbon bonds

how many carbon-carbon bonds does graphite have

3

why can graphite conduct

is has free electrons which move between layers

why does graphite have free electrons

they’re not used in bonding

what is a positively charged ion called

cation

what is a negatively charged ion called

anion

what crystal structure is ice

simple molecule

what crystal structure is iodine

simple molecule

what crystal structure is magnesium

metallic

what crystal structure is sodium chlorides

ionic

what structure does metallic bonding take

a lattice

describe metallic bonded structures

a lattice of positively charged ions surrounded by a sea of delocalised electrons

what forces do metallic bonds have

strong electrostatic forces

what are the electrostatic forces between in a metallic bond

oppositely charged ions

what would a greater charge on the ions cause

a stronger attractive force

what would larger sized ions cause

weaker attraction due to atomic radius

why do metallic bonded chemicals conduct

because electrons are free to move

define coordinate bonding

both electrons in a covalent bond donate to one atom

what is dative covalent bonding

coordinate bonding

what groups are covalently bonded

group 4 5 6 7 8 non metals

what two elements can covalent bonds form between

non-metals

how can covalent bonds be shown

in dot and cross diagrams

what type of forces do covalent bonds have

strong electrostatic forces