Chapter 6 - shapes of molecules and intermolecular forces

Question 1

Wedges

Answer 1

➜ a solid line = ━ represents a bond
➜ a solid wedge = ▲ comes out the plane of paper
➜ a dotted wedge = ┋ goes into the plane of paper

Question 2

Bonded and Lone pair repulsions

Answer 2

➜ lone pair of electrons are slightly closer to central atom and occupies more space than bonded pair
➜ lone pairs repel more strongly than bonding pairs

Question 3

2 bonded No lone pair

Answer 3

➜ Linear
➜ angle = 180
➜ e.g CO₂ & BeF₂

Question 4

3 bonded No lone pair

Answer 4

➜ Trigonal Planar
➜ angle = 120
➜ e.g SO₂ & BF₃

Question 5

4 bonded No lone pair

Answer 5

➜ Tetrahedral
➜ angle = 109.5
➜ e.g NH₃ & CH₄

Question 6

5 bonded No lone pair

Answer 6

➜ Trigonal Bipyrmaidal
➜ angle = 120, 90
➜ e.g PF₅ & PCl₅

Question 7

6 bonded No lone pair

Answer 7

➜ Octahedral
➜ angle = 90
➜ e.g SF₆ & SeF₆

Question 8

2 bonded 2 lone pair

Answer 8

➜ Bent or non linear
➜ angle = 104.5
➜ e.g H₂O & SCl₂

Question 9

3 bonded 1 lone pair

Answer 9

➜ Pyramidal
➜ angle = 107
➜ e.g NH₃

Question 10

4 bonded 2 lone pair

Answer 10

➜ square planar
➜ angle = 90

Question 11

Electronegativity

Answer 11

➜ the attraction of a bonded atom for the pair of electrons in a covalent bond

Question 12

Electronegativity Increases across period

Answer 12

➜ effective nuclear charge increases across a period
➜ atomic radius decreases
➜ the shell distance stays same

Question 13

Electronegativity decreases down a group

Answer 13

➜ more shielding of electrons = atomic radius increases = nuclear charge increases down a group, but the effective nuclear charge does not as it is negated

Question 14

Polar bond

Answer 14

➜ a covalent bond between atoms with different electronegativities with positive and negative partial charges on the bonded atoms
➜ the shared pair of electrons is shared unequally between bonding atoms

Question 15

Non Polar bond

Answer 15

➜ shared pair of electrons shared equally between bonded atoms

Question 16

Dipole

Answer 16

➜ positive and negative partial charges separated by a short distance in a molecule

Question 17

most electronegative element

Answer 17

➜ Fluorine is the most electronegative element

➜ The closer an element is to Fluorine the more electronegative the element

Question 18

London Forces (induced dipole dipole)

Answer 18

➜ weakest
➜ exist between non polar and polar
➜ movement of electrons produces a changing dipole in a molecule
➜ instantaneous dipole induces a dipole on neighbouring molecule
➜ only temporary
➜ more electrons = stronger london forces

Question 19

Permanent dipoe dipole interactions

Answer 19

➜ permanent between polar molecules

➜ can exist with london forces asw

Question 20

Simple molecular substances

Answer 20

➜ molecules held by weak intermolecular forces

➜ ATOMS with in each molecule bonded together by STRONG covalent bonds

Question 21

Properties of simple molecular

Answer 21

➜ low melting and boiling = weak intermolecular forces ez to break (covalent doesnt break)
➜ polar may dissolve in polar
➜ non conductors

Question 22

Hydrogen Bonding

Answer 22

➜ special type of permanent dipole dipole interaction

➜ occur between to an electronegative atm (F, O, N)

Question 23

Ice is less dense than water

Answer 23

➜ lattice structure of ice due to hydrogen bonds so it can float
➜ ice melts = lattice collapses = allowing molecules to move closer and increasing density

Question 24

H₂O has high melting//boiling point

Answer 24

➜ strong H bonds and energy required