bonding (phys I)

Question 1

why does bonding occur?

Answer 1

so elements obtain a noble gas structure

(no charge)

Question 2

ionic bonding

Answer 2

• occurs when 2 elements have a large diff. in electronegativity
• result of strong es. forces of attr. between oppositely charged ions

Question 3

structure of ionic compounds

Answer 3

giant, regular lattice

Question 4

properties of ionic compounds

Answer 4

• high m.p –> strong es. forces of attr. –> lots of energy needed
• only conducts electricity if molten or dissolved in sol. (ions free to move & carry charge)
• brittle –> oppositely charged ions repel each other if adj

Question 5

metallic bonding

Answer 5

result of es. forces of attr. between +ve metal ions & sea of delocalised electrons

Question 6

structure of metallic compounds

Answer 6

giant lattice of +ve metal ions with delocalised electrons moving in between

Question 7

properties of metals

Answer 7

• high mp –> strong es. forces –> lots of energy needed
• conducts electricity –> delocalised electrons can move & carry charge
• malleable –> attr. similar in all directions –> planes of ions can slide over each other
• shiny

Question 8

covalent bonding

Answer 8

• occurs when 2 elements have small diff. in electronegativity
• electron pair shared between 2 atoms

(forms either simple molecule or macromolecule)

Question 9

define dative cov. bonding

(or coordinate cov. bonds)

Answer 9

a cov. bond in which both electrons are donated from the same atom

(in diagrams, arrows used to represent dative cov. bonds)

Question 10

properties of simple covalent molecules

Answer 10

• can be solids, liquids, gases
• low m.p –> helt together by weak WDWs –> little energy needed
• can’t conduct electricity

Question 11

specific types of macromolecules

Answer 11

• graphite
• diamond
• iodine
• ice

Question 12

structure of graphite

Answer 12

C atom cov. bonded to 3 others –> trigonal planar shape

Question 13

properties of graphite

Answer 13

• high m.p –> many strong cov. bonds
• conducts electricity –> delocalised electrons between layers
• soft –> weak VDWs between layers –> can slide over each other

Question 14

struc of diamond

Answer 14

C atom cov. bonded to 4 others –> all repel each other –> tetrahedral shape

Question 15

properties of diamond

Answer 15

• high m.p –> many strong cov. bonds
• doesn’t conduct electricity
• hard

Question 16

define electronegativity

Answer 16

the power of an atom to attract a pair of electrons

Question 17

why does electronegativity increase across a period?

Answer 17

no. of protons increases –> atomic radius decreases

Question 18

types of intermolecular forces

Answer 18

• VDWs (temp dipole-dipole induced attractions)
• permanent dipole-dipole forces
• hydrogen bonds

Question 19

how do VDWs arise between molecules?

Answer 19

1. electronic distribution in molecule = asymmetrical due to random movement of electrons –> cause temp. dipole
2. temp dipole induced in neighbouring molecule
3. temp dipoles attracted to each other

Question 20

permanent dipole-dipole forces

Answer 20

• occurs in polar molecules –> molecules must have sig. diff in en.
• stronger than VDWs (& occurs in addition to them)

Question 21

hydrogen bonds

Answer 21

• occurs when hydrogen is directly bonded to N,O,F
• strongest im force

(when drawn, lone pair needs to be shown on N,O,F & draw partial charge)