chapter 6 shapes of molecules, electronegativity and polarity

Question 1

Electron pair repulsion theory

Answer 1

Pairs of electrons around a central atom repel each other so they move as far appart as possible to minimise this repulsion

Question 2

What causes molecules to have shapes

Answer 2

electron pair repulsion theory

Question 3

What does a solid line represent in 3d drawings

Answer 3

a bond in/on the plane of the paper

Question 4

what does a solid wedge represent

Answer 4

a bond that comes forwards out of the plane of the paper

Question 5

what does a dotted wedge represent

Answer 5

a bond that goes backwards into the plane of the paper

Question 6

Greatest bond angle possible and shape of molecule with 2 regions of electron density

Answer 6

180 deg, linear

Question 7

Region of electron density?

Answer 7

Essentially just the covalent bonds. Double and tripple bonds count as one region

Question 8

Shape of molecule with 3regions of electron density around central atom?

Answer 8

trigonal planar, 120 deg. bond angle

Question 9

planar?

Answer 9

flat

Question 10

Shape with 4 regions

Answer 10

Tetrahedral, bond angle of 109.5 deg

Question 11

shape of a molecule with 5 regions..

Answer 11

trigonal bipyramidal arrangement. 3, 120deg bond angles and 2, 90deg bond angles

Question 12

shape of molecule with 6 regions..

Answer 12

octahedral. 90deg bond angles

Question 13

lone pair repulsion compared to bonded pair

Answer 13

lone pair is slightly closer fo central atomand occupies more space than a bonded pair so repels more than a bonded pair

Question 14

Effect of lone pairs on bond angles

Answer 14

Each lone pair reduces the bond angle by 2.5 deg

Question 15

shape of molecule with 3:1 bonded: lone pairs

Answer 15

pyramidal e.g ammonium

Question 16

shape of molecule with 2:2 bonded:lone pairs

Answer 16

nonlinear e.g H2O

Question 17

electronegativity? (pauling value)

Answer 17

measure of the ability of an atom in a molecule to attract a pair of electrons in a covalent bond to itself

Question 18

meaning of a high electronegativity value

Answer 18

bonding electrons are attracted more strongly to that atom

Question 19

trends of electronegativity on the periodic table x2

Answer 19

it increases going up a group (bottom to top)
It increases across a period (left to right)

Question 20

Most electronegative atoms?

Answer 20

fluorine (most), nitrogen, oxygen, chlorine

Question 21

what causes the electronegativity to increase across a period

Answer 21

higher pos charge of nucleus gives it a stronger attraction for neg charged bonding pair of electrons

Question 22

what causes electronegativity to increase up a group

Answer 22

The bonding pair are closer to the nucleus (outer shell is closer)
There are fewer shielding inner shells

Question 23

non polar bond/ pure covalent?

Answer 23

Bonded electron pair is shared equally between the atoms

Question 24

when do we get non polar bonds/ pure covalent

Answer 24

when bonded atoms are the same
or the bonded atoms have the same or similar electronegativity values

Question 25

polar bond

Answer 25

bonded electron pair is shared unequally between bonded atoms

Question 26

How do we represent polar bonds.

Answer 26

Delta symbol (partial charge). The atom to which the bonding pair is attracted will be partially negative and the other atoms partially positive.

Question 27

Dipole meaning and situation?

Answer 27

The separation of opposite charges. This is said of a polar bond e.g HF has a dipole

Question 28

what increases the polarity of a bond and the ionic character

Answer 28

a greater difference in electronegativity.

Question 29

what does a difference in polarity of more than 1.8 in a molecule produce

Answer 29

Full ions, we get ionic bonding instead

Question 30

how do we represent permanent dipoles

Answer 30

An arrowhead pointing towards the partially negative atom with a plus symbol merged with the other end of the arrow

Question 31

polar molecule

Answer 31

A molecule with a permanent dipole acting in one direction

Question 32

in which situations would the charge of dipoles cancel out and what does it leave

Answer 32

In a molecule with symmetrically opposing dipoles leaving a n overall non polar molecule

Question 33

Which characteristics produce a polar molecule

Answer 33

Asymmetrical molecule since the dipoles dont canel out

Question 34

What allows ionic compounds to dissolve in polar solvents (especially water)

Answer 34

The polar molecules of the solvent can form strong enough attractions to ions to permit dissolving

Question 35

what is it about the formation of ion dipole bonds that permits the dissolving of some ionic compounds

Answer 35

Energy is released

Question 36

In which cases can polar solvents not dissolve ionic compounds

Answer 36

If the combined strength between ions in the solid lattice and the attraction between the polar molecules themselves is stronger than that of the attraction between the dipoles and the ions

Question 37

what 3 factors can solubility be dependant upon

Answer 37

amount of solute/solvent, temperate

Question 38

solubility of nitrates

Answer 38

all are soluble

Question 39

solubility of chlorides

Answer 39

all except AgCl and PbCl2

Question 40

solubility of sulfates

Answer 40

most except BaSO4, PbSO4 and SrSO4

Question 41

solubility of catbonates

Answer 41

All INsoluble except (NH4)2CO3, and carbonated of G1

Question 42

solubility of G1 andd ammonium salts

Answer 42

All soluble

Question 43

is C-H bond polar or nonpolar

Answer 43

non polar at a level