Chemical Bonding

Question 1

What are the Nobel gases?

Answer 1

Helium
Neon
Argon
Krypton
Xenon
Radon

Question 2

Key properties of the Nobel Gases

Answer 2

8e- in outer shell
very stable
most unreactive of all elements
monatomic
don’t usually form bonds with other elements
fulfil Lewis Octet rule
8 e- in valence shell (8e- in s and p orbitals)

Question 3

define: valence shell

Answer 3

outermost occupied shell of an atom
highest principle quantum umber
e- are most likely to participate in bonding

atoms with valence shell not will form chemical bonds

Question 4

types of e-

Answer 4

core e-
valence e- (only important in bonding)

Question 5

define: ionic bond

Answer 5

electrostatic attraction forms between oppositely charged ions
arises from transfer of e- between atoms

Question 6

define: covalent bond

Answer 6

shared pair of e- between atoms

Question 7

ionic bonding; losing e-

Answer 7

more H+ than e-
positive charge
called positive ions or cations
generally s & d block elements

Question 8

ionic bonding; gaining e-

Answer 8

more e- than H+
negative charge
called negative ions or anions
generally p block elements

Question 9

Example of ionic compound
Sodium Chloride

Answer 9

Ions held together by electrostatic forces
contains one cation and one anion - neutral charge

ionic compounds have neutral charge
toral charge of anions and cations must be equal

ionic compounds form giant 3D structures called ionic lattices

Question 10

covalent bonding

Answer 10

many elements exist as molecules
held together by a covalent bond
simple diatomic molecules

Different elements combine to form covalent bonds
Represented by lines or wedges

Question 11

covalent bonding: fluorine

Answer 11

requires 1e- for full outer shell
forms diatomic fluorine
single F-F bond

Question 12

covalent bonding: chlorine

Answer 12

requires 1e- for full valence shell
forms diatomic chlorine
single cl-cl bond

Question 13

covalent bonding: oxygen

Answer 13

requires 2e- for full outer shell
forms diatomic O2
double O=O bond

Question 14

covalent bonding: nitrogen

Answer 14

requires 3e- for full outer shell
forms diatomic N2
Triple N-N bond

Question 15

define: electronegativity

Answer 15

describes the power of an atom in a molecule to attract e- towards itself
has no units

high electronegativity = pulls e- more strongly towards itself
low electronegativity = pulls e- more weakly towards itself

Question 16

what are the most electronegative element?

Answer 16

nitrogen
oxygen
fluorine
chlorine

Question 17

periodic property

Answer 17

electronegativity dependent on position of an element in periodic table

nuclear charge
atomic radius
e- shielding

Question 18

atom has higher electronegativity if it has?

Answer 18

higher nuclear charge
small atomic radius
low amount of shielding

Question 19

how to predict bond ionic or covalent

Answer 19

calculate difference in values of electronegativity

Question 20

predict ionic?

Answer 20

difference has to be GREATER than 1.7

Question 21

predict covalent?

Answer 21

difference has to be LESS than 1.7

Question 22

Polar bonds - hydrogen chloride

Answer 22

special case

gaseous- H and Cl are covalently bonded - polar covalent bond
aqueous- ionises completely H+ and Cl-

electronegativity difference 0.9

Question 23

covalent or ionic scale of bonding

Answer 23

ionic or covalent tend to have different properties

can predict via:
boiling point
melting point
solubility in water
electrical conductivity

Question 24

further ionic bonding

Answer 24

some atoms behave as a single entity when they are a compound:

phosphate -3
sulphate -2
carbonate -2
nitrate -1
hydroxide -1
ammonium +1

Question 25

further covalent bonding

Answer 25

not all e- need to be covalently bonded to fill valence
unbounded pairs of e- are lone pairs

lone pairs can be shared with ions
forming dative covalent bonds

Question 26

what is a dative covalent bond?

Answer 26

a bond where a lone pair of e- is shared with an ion

Question 27

describe why atoms form chemical bonds

Answer 27

unfilled valence orbitals will form chemical bonds with other atoms
to fulfil octet rule with 8e- in valence shell

Question 28

predict type of bond formed between atoms depending on?

Answer 28

position of elements in periodic table
difference in electronegativity (ionic or covalent)
electronic configuration (single, double, triple covalent)