Periodic Table of the Elements
1
These are all metals, they are made up of positive ions in a sea of electrons.
Potassium is made up of 1+ ions, Calcium is made up of 2+ ions and scandium is made up of 3+ ions.
K1+ ­
K1+ ­
­
K
1+ K
1+ Ca2+ Ca2+ ­
­
Ca
­
­
2+ ­
­
­
Sc3+
Sc3+
12e­
­
Sc3+
Sc3+
Ca2+ ­
As the charge and number of electrons in the sea increase so does the intermolecular force. The highest MP is expected for Sc, the lowest K.
2
These all ionic solids made up of oppositely charged ions.
Bigger the magnitude of attraction higher the MP
Na1+ O
Mg2+ O2­ Mag 4 force
Al3+ O2­ Mag 6 force
2­ Mag 2 force
F = kq1q2/r2
lowest MP
highest MP
3
All are ionic solids. They all have a mag 4 force so we must compare sizes of ions to establish the ionic radius between adjacent ions. Be2+ has 1 energy level, Ca2+ has 3 energy levels and Ba2+ has 5 energy levels. The further away the ions are the weaker the force the lower the melting point. The highest MP is for the sulfide of Be, the lowest MP is for BaS.
4
All 3 of these nonmetals have potential oxidation states of 3 and 5. If the 5+ oxidation state is used they are all 550 molecules (trigonal bipyramidal) and nonpolar so the main force of attraction is LDF which gets bigger as molecules get bigger.
SbH5 has the biggest molecules and NH5 has the smallest. The trend shown has an anomaly. You do not expect the NH5 to have a higher MP. It does do to the additional H bonding occuring between molecules.
5
Dipole ­ Dipole forces between polar molecules are stronger than LDF between non polar molecules.
6
These are all nonpolar molecules with LDF which get larger as molecules get larger. The largest LDF are for C15, the smallest for C5. The highest MP is for C15, the lowest for C5.
7
ionic, polar molecular, non polar molecular, metallic and covalent network.
8
Both are covalent network crystals with strong covalent bonds. Each C in graphite is bonded to 3 neighbours with 1 delocalized bond per C. This delocalized bond allows the electrons to move between sheets of graphite making soft and a semi conductor.
Diamond has C atoms with 4 covalent bonds per C atom making it one of the strongest material know to man.
graphite
delocalized bonds are free electrons like metallic bonds
delocalized bonds are free electrons like metallic bonds
Diamonds ­ There are no loose electrons in diamonds. They are non conductors and the hardest materials known.
9
These are all polar molecular substances due to the OH bonds. There are H bonds betwen the OH groups of adjacent molecules. The more OH groups the greater the H bonding. 1, 2 and 3 OH groups/ molecule. The greater the number of OH groups the higher the MP.
10
The more OH groups the more viscous.
11
They are hard because ionic bonds are very strong.
If pressure is applied to a specific area the ions can move until like charged ions are adjacent at which point the crystal shatters.
12
These are all metallic crystals with positive ions in a sea of electrons.
Transition metals have higher MP due to ions with greater charges and more electrons in the sea of electrons.
13
a) metallic
b) covalent network crystals
c) non polar molecular
d) metallic
e) ionic
f) covalent network
g) ionic
14
Silicon is a covalent network crystals with strongest intermolecular forces so it has a very high MP.
The rest in this period are non polar molecular crystals with LDF forces which get bigger with the size of the molecules. MP arranged from lowest to highest
Ar,Cl2,P4,S8, Si
15
The C ­ H bond is very strong so it takes a lot of energy to break it (intramolecular force)
The intermolecule forces are LDF which are weak.
Strong force ­ intramolecular
weak forces intermolecular
16
Metallic bonds have mobile electrons which are flexible. Ionic bonds are strong and inflexible due to the immobility of the ions.
17
CO2 are nonpolar molecular crystals with weak LDF between nonpolar molecules.
SiO2 are covalent network crystals with very strong covalent bonds.
18
Periodic Table of the Elements
consecutive
A B C D
monatomic gas
unreactive
a) C b) MC, ionic compound, high MP, BP, soluble in water
c,d) AH3 (pyramidal), BH2 (angular), CH (linear) e) non conductive, nonpolar molecular crystals
19
All are ionic solids mag 1 forces between ions.
Larger ions are further apart so the force gets weaker. Most soluble are the largest ions. Iodide ion is the largest and F ion is the smallest.
CsF has much larger Cs ions so ionic force is smaller than NaF. CsF is easier to pull apart so it is more soluble in water and has a lower MP.
20