6. Bonding

Question 1

ionic bonding

Answer 1

• the sum of all electrostatic attractions between oppositely charged ions
• resulting from the transfer of electrons from one bonding atom to another

Question 2

lattice energy

Answer 2

energy given out when ionic bond is formed

Question 3

polyatomic ions

Answer 3

• ammonium (NH4+)
• hydroxide (OH-)
• nitrate (NO3-)
• hydrogencarbonate (HCO3-)
• carbonate (CO32-)
• sulfate (SO42-)
• phosphate (PO43-)

Question 4

characteristics of ionic compounds

Answer 4

• crystalline at room temperature
• have high melting and boiling points
• conduct electrical current in molten or solution state (not in solid)
• polar bonds (dissolve in polar solvents)

Question 5

metallic bond

Answer 5

• electrostatic attraction between a lattice of positive metal ions and delocalized electrons
  (e- in random movement except when connected to a source)

Question 6

strength of metallic bonds depends on

Answer 6

• number of valance electrons that become delocalized
• charge of the metal ion
• ionic radius of the metal ion

Question 7

alloys

Answer 7

• homogeneous solution of a metal in another metal
• steel, brass, pewter

Question 8

characteristics of metallic compunds

Answer 8

• melting point decreases as ionic size increases
• malleability (can be beaten into shape)
• ductility (can be drawn into a wire)
• electrical conductivity

Question 9

covalent bonds

Answer 9

• chemical bond resulting from the sharing of electrons between two bonding atoms (formed between non-metals, except beryllium)
• electrostatic attraction between a shared electron pair and positively charged nuclei
• obeying the octet rule and sharing of electrons
• electrons in the bond move back and forth so that each atom has a stable outer E level for some time

Question 10

ionic
polar covalent
non-polar/pure covalent

Answer 10

x>1.8
0>x>1.8
x=0

Question 11

polar vs non-polar molecules

Answer 11

non-polar molecules have an even distribution of charge in the molecule due to an equal sharing of bonding electrons (no electronegativity difference) - the opposite for polar

Question 12

coordinate bonding

Answer 12

or dative bonding
- when the electrons in a shared electron pair come from only one atom

Question 13

VSEPR theory

Answer 13

electrons are organized in electron domains on the furthest possible stable distance from one another
LP-LP>LP-BP>BP-BP

Question 14

electron domain

Answer 14

one direction in space/region of electron density

Question 15

lewis structures (list, state the bonding angle, LP, BP and draw each)

Answer 15

1) Linear (1)
2) Trigonal planar
3) Angular/bent (1)
4) Tetrahedral
5) Trigonal pyramidal
6) Angular/bent (2)
7) Trigonal bipyramidal
8) Seesaw
9) T-shaped (1)
10) Linear (2)
11) Octahedral
12) Square pyramidal
13) Square planar
14) T-shaped (2)
15) Linear (3)

Question 16

covalent bonding leads to two kinds of molecules

Answer 16

1)giant structures (strong covalent bonds forming a network, high MP and BP)
2) simple molecular structures (few covalent bonds, low MP and BP, exist as gases and low boiling liquids)

Question 17

characteristics of covalent compounds

Answer 17

• have a definite and predictable shape
• very strong but weaker than metallic and ionic
• low MP and BP

Question 18

molecular substances

Answer 18

• subgroup of covalent bonding
• a substance that has atoms held together by weak covalent bonds
• low MP and BP
• fullerene (allotropic modification of C, conductor)

Question 19

network solids

Answer 19

• subgroup of covalent bonding
• a solid that has covalently bonded atoms linked in one big network/macromolecule/lattice structure
• graphite (stacked graphene sheets of linked hexagonal rings, conductor), diamond (tetrahedral structure, strong bonds insulator), graphene (single layer of hexagonal C-atom lattice), SiO2 (giant covalent structure, doesn’t conduct)

Question 20

intermolecular forces

Answer 20

attractive forced between molecules (much weaker than intramolecular)

Question 21

Van der Waals

Answer 21

also called London forces or dispersion forces
- due to random movement of electrons leading to the formation of (temporary) instantaneous dipole and hence induced dipoles in molecules
- strength depends on molar mass
- effective only over a short range
- depends on the SA of the molecule

Question 22

dipole-dipole

Answer 22

• due to electrostatic attraction between molecules with permanent dipoles
• significantly stronger than VdW

Question 23

hydrogen bonding

Answer 23

• in molecules where H is bonded to an atom of high electronegativity value
• the strongest of all intermolecular forces
• important for DNA base pairing, secondary structure of proteins (alpha helix and beta pleated sheets)

Question 24

ion-dipole forces

Answer 24

• attraction forces between an ion and a polar molecule (dipole)

Question 25

resonance hybrids (list and draw)

Answer 25

1) carbonate ion 2) nitrate ion 3) sulfur dioxide 4) ozone 5) benzene 6) ethanoate ion

Question 26

sigma bonds vs pi bonds

Answer 26

sigma bonds - formed when two atomic orbitals overlap in one small area (s-s, s-p, p-p) pi bonds - formed as a result of sideways overlapping of parallel p orbitals in two areas (p-p)

Question 27

delocalization of electrons

Answer 27

happens whenever double and single bonds alternate between atoms - resonance bonding (1.5 bonds) - resonance structures (conductors)

Question 28

ozone layer

Answer 28

- stratospheric ozone is in dynamic equilibrium with oxygen (continuously being formed and decomposed by UV radiation - protecting the Earth's surface from it) - formed oxygen atoms are called radicals and they react with O2 molecules to form ozone: O=O -> 2O* O2 + O* -> O3 and vice versa: O3 -> O2 + O* O3 + O* -> 2O2 - steady-state - rate of O3 production is equal to the rate of its decomposition

Question 29

how is the steady state altered and by whom

Answer 29

by O3-depleting pollutants - CFCs and oxides of nitrogen 1) CFCs - weak C-Cl bonds broken by UV CF2CL2 -> CF2Cl* + Cl* (radical initiation) Cl* + O3 -> ClO* + O2 2) nitrogen oxides NO + O3 -> NO2 + O2

Question 30

free radicals

Answer 30

have an unpaired electron(s) - very reactive

Question 31

wavelength =

Answer 31

(h*c)/E

Question 32

hybridization

Answer 32

merging of s and p orbitals (they meet on the same energy level): sp3, sp2, sp

Question 33

formal charge

Answer 33

charge of every atom in the structure valance electrons (theoretical) - actual number of electrons surrounding it (actual value)

Question 34

how are all bonds ranked by strength

Answer 34

metallic and bonding > covalent > ion-dipole > H-bonds > dipole-dipole > VdW

Question 35

electron domain vs molecular shape

Answer 35

electron domain shape - lone electrons are regarded as bonds (not the case in molecular shape)