Structure and Bonding

Question 1

What do substances with high and low melting points have?

Answer 1

substances with high melting points have strong forces of attraction between atoms and low melting point shave weak forces of attraction between molecules

Question 2

What are the strength of forces and arrangements of particles in solids, liquids and gases

Answer 2

giants solids- with ionic and covalent bond are solids with high melting points. particles r in a fixed arrangement, do not move and vibrates.

molecular solids- have low melting points but forces r strong between molecules. particles r in a fixed arrangement, do not move and vibrates.

liquids- have low melting points but forces r strong between molecules. particles r close tgt but r arranged randomly, they slide over each other

gases- hv low melting and boiling points. particles r far apart and move randomly.

Question 3

What is a covalent bond?

Answer 3

a covalent bond is the force of attraction between the nuclei of two neighbouring atoms and a pair of electrons shared between them. they r very strong takes a lot of energy to break them apart.

Question 4

Describe covalent bonding

Answer 4

formed by the overlap of atomic orbitals. each orbital which combines contributes an unpaired electron to the bond, the joined orbital is called a molecular orbital. the greater the overlap of the atomic orbital, the stronger the covalent bond is

Question 5

What is a sigma bond?

Answer 5

a sigma bond is the overlap of atomic orbitals about a line drawn between the two nuclei. electron density is found symmetrically about a line drawn joining the two nuclei

Question 6

What is a pi bond?

Answer 6

a pi bond is the sideways overlap of p orbitals. electron density is not found symmetrically about a line drawn joining the two nuclei.

Question 7

How is a single bond represented?

Answer 7

a shared pair of electrons in a single bond is represented by a single line

Question 8

What are lone pairs?

Answer 8

are electron pairs in the outer shell that do not take part in bonding

Question 9

What do dot and cross diagrams show?

Answer 9

show how electrons are paired together in a molecule or ion

Question 10

What are electron deficient molecules and expanded octet

Answer 10

are atoms in a compounds that have less that 8 electron in the outer shell. expanded octet has more than 8 electrons in the outer shell.

Question 11

What is coordinate/ dative covalent bond

Answer 11

is where one atom provides both electrons for the covalent bond. for it to occurs need the first atom with lone pair of electrons and second with an unfilled orbital.

Question 12

What does displayed formula show?

Answer 12

shows the coordinate bond with an arrow. the head of the arrow points away from the atoms which donates the lone pair

Question 13

Explain ionic bonding

Answer 13

ions are formed by gaining or losing electrons, usually have a full outer shell. ionic bonding is the net attractive force between positive and negative ion. the net attractive force results in a giant ionic structure. the structure is arranged into a 3 dimensional lattice. electrostatic attractive force between ion acts in all directions and the bond is very strong

Question 14

Explain metallic bonding

Answer 14

is a lattice of positive ions in a sea of delocalised electrons. delocalised electrons are not associated with atoms or ions. they move freely between metals

Question 15

What is electronegativity? Where does it increase and decrease?

Answer 15

is the ability of an atom in a covalent bond to attract electrons in the bond to itself, it increases across a period from group 1-7, decreases down any group

Question 16

What are polar and non polar molecules? also speak about its polarity

Answer 16

if electronegative values in a covalent bond are the same its non polar, also if positive n negative coincide its non polar

if electronegative values in a covalent bond are different then its polar, if the positive and negative values do not coincide its polar

Question 17

What’s the degree of polarity measured by?

Answer 17

degree of polarity is measure using dipole movement

Question 18

What are the 3 types of intermolecular forces?

Answer 18

permanent dipole- dipole force
van der Waals forces
hydrogen bonding

Question 19

Describe the 3 intermolecular forces

Answer 19

permanent dipole- dipole- is the weak attractive force between the positive of a molecule and negative of another neighbouring molecule

van der Waals- partakes in temporarily induced dipoles

hydrogen- permanent form of dipole bonding, it required one molecule with a H atoms covalently bonded to an f, n or o atom, a second molecule with f, n or o atom with a lone pair of electrons.

Question 20

What is a lattice?

Answer 20

is a regular 3 dimensional arrangement of particles.

Question 21

What are giant structure and their 3 types?

Answer 21

are lattices with strong bonds between the particles
3 types:
ionic- sodium chloride, magnesium oxide
covalent- diamond, silicon dioxide
metallic- copper, iron

Question 22

What are the properties of ionic, covalent and metallic structures?

Answer 22

ionic:
high melting n boiling points
soluble in water
conduct electricity when molten or dissolved in water
brittle

covalent:
high melting n boiling points
insoluble in water
apart from graphite, does not conduct electricity
apart from graphite, hard

metallic:
high melting n boiling points
insoluble in water
conduct electricity when solid or molten
malleable and ductile

Question 23

Describe the properties of simple molecular substances

Answer 23

have low melting and boiling points because they have weak intermolecular forces

solubility depends of if its polar or non polar

also cannot conduct electricity