Chemical Bonding

Question 1

what is the Noble Gas Structure

Answer 1

2 (duplet configuration) / 8 (octet configuration) valence electrons: stable electronic configuration; lack of reactivity

Question 2

what is the octet rule

Answer 2

tendency for atoms to lose/gain/share electrons until there are 8 valence electrons

*exception to this rule applies to atoms with only 1 electron shell, requiring only 2 valence electrons for stability

Question 3

what is an ion

Answer 3

atom or group of atoms that have electrical charges

Question 4

what are cations and anions

Answer 4

cation: positively charged ion (lose electrons)
anion: negatively charged ion (gain electrons)

Question 5

how are cations formed

Answer 5

atoms of metals tend to form cations by losing their valence electron(s) to attain the noble gas configuration

positive charge arises as there are now more protons than electrons

*most metals have 1-3, easier to lose 1-3 than to gain 5-7

Question 6

how are anions formed

Answer 6

atoms of non-metals tend to form anions by gaining valence electron(s) to attain the noble gas configuration

positive charge arises as there are now more electrons than protons

*most metals have 4-7, easier to gain 1-3 than to gain 5-7

Question 7

3 points

what is the relationship between group number and ionic charge

Answer 7

ionic charge of an ion is dependent on number of valence electrons its atom contains

elements in the same group have the same number of valence electrons

hence, they form ions of the same charges and have similar chemical properties

Question 8

why do elements in groups 1-2, 13 form cations

Answer 8

they are metals

Question 9

why do elements in group 18 not form ions

Answer 9

they tend to be monatomic as their atoms have stable electronic structure and do not usually form compounds

Question 10

why do elements in groups 15-17 form anions

Answer 10

they are non-metals

*can also form covalent bonds

Question 11

what is ionic bonding

Answer 11

ionic bond defined as the strong electrostatic forces of attraction between the positively charged ion (metals, cations) and negatively charged ion (non-metals, anions)

Question 12

3 points

how are ionic compounds formed

Answer 12

generally occurs between atoms of metals and atoms of non-metals

involves gain/loss of electrons (transfer of electrons) to achieve stability

forms oppositely charged ions

*include legend for dot-and-cross diagrams

Question 13

what is covalent bonding

Answer 13

covalent bond defined as the electrostatic forces of attraction between the shared electrons and the 2 positively charged nuclei of the atoms

Question 14

3 points

how are covalent bonds formed

Answer 14

generally occurs between atoms of non-metals

involves sharing of electrons to achieve noble gas electronic configuration

forms molecules

Question 15

what is the structural full formula of H₂O

Answer 15

H - O - H

single bond

Question 16

what is the full structural formula of O₂

Answer 16

O = O

double bond

Question 17

what is the full structural formula of N₂

Answer 17

N ≡ N

triple bond

Question 18

2 points

why do ionic compounds have high melting and boiling points

Answer 18

they have a giant ionic crystal lattice structure

a lot of energy is needed to overcome the strong electrostatic forces of attraction between the oppositely charged ions

Question 19

2 points each

why do ionic compounds not conduct electricity in the solid state but are good conductors in the molten and aqueous states

Answer 19

in the solid state, the ions are held in their fixed positions by strong electrostatic forces of attraction
the ions are not mobile to conduct electricity

in the molten/aqueous state, the electrostatic forces of attraction are overcome
the ions are mobile to conduct electricity

Question 20

2 points

why do simple covalent/molecular substances have low melting and boiling points

Answer 20

they have a simple molecular structure

little energy is needed to overcome the weak intermolecular forces of attraction between the molecules

Question 21

1 point

why do covalent substances generally not conduct electricity at any state

Answer 21

they have no mobile charge carriers (ions/electrons) to conduct electricity