Bonding and shapes

Outline how VDW forces arise between molecules

oscillating/changing/temporary/transient dipole on one atom
causes an induced/resultant dipole on another molecule/atom

How do hydrogen forces arise between molecules of H20

O more electronegative than H/O is very electronegative
H₂O have polar molecules

Liquid HCI also has additional intermolecular forces. What are these forces?

permanent dipole-dipole interactions

electronegativity definition

'Attraction of an atom for the electrons in a covalent bond'

Why is HCl a polar molecule but CCl4 is a non polar molecule

Cl is more electronegative (than H or C)
CCI4 is symmetrical
In CCI4 dipoles cancel

Two anomalous properties of water

Ice is lighter than water
H bonds hold H₂O molecules apart/H-bonds are longer
Higher melting/boiling point than expected
strength of H bonds that need to be broken
High surface tension/viscosity
due to strength of H bonds across surface

explain why NH3 has bond angle of 107

electron pairs repel other electron pairs
lone pair has more repulsion

electronegativity definition

The ability of an atom to attract electrons
in a covalent bond

Molecules of BF3 contain polar bonds but the molecules are non-polar. explain why

BF3 is symmetrical
The dipoles cancel out

covalent bond meaning

shaired pair of electrons

Name which type of bond is formed when a molecule of BF3 reacts with an F- ion

Coordinate/ dative (covalent)
(Lone) pair of electrons/ both electrons (on F)
Donated from F"/ fluoride or donated to the BF3

Why is the boiling point order Br₂ > NH₃ > F₂?

M1: NH₃ has hydrogen bonding
M2: F₂ and Br₂ have temporary dipole-induced dipole forces
M3: Forces are intermolecular for NH₃

explain in terms of electronegativity why the boiling point of H2S2 is lower than H2O2

Electronegativity of S lower than O
No hydrogen bonding between H₂S2 molecules
OR
Or only wan der vaal forces/ dipole-dipole forces between H₂S

explain conductivity and melting point of ice

does not conduct:
no mobile charge carriers/electrons/ions
structure/bonding:
H-bonds/intermolecular forces/ simple molecular
melting point:
Low because H bonds/intermolecular/weak forces between molecules (are broken)

how does a giant metallic structure conduct electricity

electrons move

why do giant covalent structure have higher boiling point than simple molecular structure

giant has stronger forces
giant: covalent bonds break
simple: molecules/intermolecular forces break / van der Waals break

why does silicon have high melting point

giant covalent
Many/strong covalent bonds
Bonds must be broken/overcome

Why is melting point of sulfur higher than phosphorous

Both are (Simple) molecular substances
S bigger molecule (than P)
So more/ stronger van der Waals' forces (to be broken or overcome)

why is melting point of aluminium higher than sodium

Bigger charge (3+ compared to 1+)
smaller atom/ion in Al / more protons/bigger nuclear charge
More free /delocalised electrons (in Al)
Stronger metallic bonding

which non-metals are giant covalent lattices

Carbon
silicon
silicon dioxide

Explain in terms of their structure and bonding

why the boiling point of phosphorus is much lower than that of silicon

Why are ionic structures soluble

Water is polar/water has a dipole/ions interacts with water molecules

Why are covalent structures insoluble

no interaction with water/no intermolecular forces with water/graphite is non-polar

What to mention when talking about graphite

has layers

What is meant by ionic lattice

Repeating pattern
of oppositely charged ions

when do non-metals start in periodic table

start at boron. continues down in staircase

What is the trend in electronegativity across a period?

Electronegativity increases across a period.

Why does electronegativity increase across a period?

Nuclear charge increases while atomic radius decreases

What is the trend in electronegativity down a group?

Electronegativity decreases down a group.

Why does electronegativity decrease down a group?

Atomic radius increases and shielding increases

What is electronegativity?

The ability of an atom to attract electrons in a covalent bond.

How does nuclear charge affect electronegativity?

Higher nuclear charge increases electronegativity because the nucleus attracts bonding electrons more strongly.

How does atomic radius affect electronegativity?

Larger atomic radius decreases electronegativity as bonding electrons are further from the nucleus.

How does electron shielding affect electronegativity?

More shielding decreases electronegativity because inner electrons reduce the attraction between the nucleus and bonding electrons.

Why does PCl₄ have a +1 charge?

PCl₄⁺ forms when phosphorus bonds with four chlorine atoms and loses one electron

Why does PCl₆ have a -1 charge?

PCl₆⁻ forms when phosphorus bonds with six chlorine atoms and gains one extra electron to complete the bonding

Does Boron tribromide conduct

Boron tribromide does not conduct in solid and molten states
Boron tribromide has no mobile electrons OR no (mobile) ions

How do you show dative bond

with arrow

How do you show a covalent compound has negative charge using 3d drawing

draw brackets around it with -