3.2 Inorganic Chemistry Flashcards
3.2.1.2 Physical properties of period 3 elements
What happens to the atomic radius in period 3 elements?
The atomic radius decreases from left to right
because the increased n.o of protons creates more positive charge attraction for electrons which are in the same shell with the same shielding.
3.2.1.2 Physical properties of period 3 elements
Explain the melting points for Na, Mg and Al.
Metallic bonding.
General increase in mp as metal ions have an increasing + charge, increasing **n.o of delocalised electrons **and smaller ionic radius.
|> stronger metallic bonding.
High energy needed to break these bonds.
3.2.1.2 Physical properties of period 3 elements
Explain the melting point for Silicon (Si).
Has the highest mp/bp.
Has a giant covalent structure/ macro-molecular.
**Many strong covalent bonds **hold the Si atoms together.
High energy needed to break these bonds.
3.2.1.2 Physical properties of period 3 elements
Explain the melting point for Phosphorus (P4).
Has a lower mp than silicon due to weaker simple molecular structures.
MP determined by weaker VDW forces.
Little energy needed to break P4.
3.2.1.2 Physical properties of period 3 elements
Explain the melting point for Sulfur (S8).
Has a **higher mp than P4 **due to larger simple molecular structures.
Has larger VDW forces and hence a higher mp.
High energy needed to break S8
3.2.1.2 Physical properties of period 3 elements
Explain the melting point for Chlorine (Cl2).
Has a lower mp than P4 and S8 due to smaller simple molecular structures.
Has smaller VDW forces and hence a lower mp
Less energy needed to break Cl2.
3.2.1.2 Physical properties of period 3 elements
Explain the melting point for Argon (Ar).
is monoatomic.
Has a lower mp due to it only existing as individual atoms.
Has smaller VDW forces .
Little energy needed to break Ar.
3.2.2 Group 2 the alkaline earth metals
What is ionisation energy?
The minimum amount of energy required to remove 1 mole of electrons from 1 mole of atoms in a gaseous state of an element to form one mole of gaseous ions.
3.2.1.2 Physical properties of period 3 elements
Explain the trend in ionisation energy in period 3 elements.
General trend
- increases } increasing n.o of protons as electrons are being added to the same shell.
- The more electron shells between **+ nucleus **and **- electrons **are removed the less energy is needed, weaker attraction.
- The more protons in the nucleus, the bigger the attraction between nucleus and outer electrons, more energy required to remove the electron.
- The bigger the atom, the further away the outer electron is from the nucleus, attractive force reduces between outer E and N, easier to remove electrons.
3.2.1.2 Physical properties of period 3 elements
State the first ionisation energy for Sodium (Na).
**Na (g) → Na+ (g) + e- **
1st I.E = +495.8 KJmol-1
I.E always requires energy, endothermic process, and have a + values
3.2.1.2 Physical properties of period 3 elements
What is successive ionisation?
The removal of more than one electron from the same atom.
3.2.1.2 Physical properties of period 3 elements
State an example of the successive ionisation ionic equation with Magnesium (Mg).
**Mg+ (g) → Mg 2+ (g) + e- **
2nd I.E = +1450 kJmol-1
There’s a jump in energy in the 3rd and 11th electrons as removing electrons from shell closer to nucleus.
General increase in energy as removing an electron from an increasingly more + ion.
3.2.1.2 Physical properties of period 3 elements
Why does the first ionisation energy increase across a period?
- N.o of protons in the nucleus increase, increase in nuclear attraction.
- Shielding is similar.
- Increased charge on the nucleus means that it gets increasingly difficult to remove an electron, more energy is required.
3.2.1.2 Physical properties of period 3 elements
Why does the first ionisation energy decrease going down a group?
Atomic radius increases as we go down the group.
Outer e- are further away from the nucleus.
Attractive force is weaker.
**Less energy **required to remove an electron.
3.2.1.2 Physical properties of period 3 elements
Why is Aluminium’s first ionisation energy lower than Magnesium?
A decrease for Aluminium is evidence that atoms have sub-shells.
The outer electron in Al sits in a higher energy sub-shell slightly further from the nucleus than the outer electron of Mg.
Mg- 1s2, 2s2, 2p6, 3s2
Al- 1s2. 2s2, 2p6, 3s2, 3p1.
3.2.1.2 Physical properties of period 3 elements
Explain the drop in the first ionisation energy between group 5 (P4) and group 6 (S8) .
**A decrease at sulfur is evidence for electron repulsion in an orbital. **
Phosphorus: 1s2, 2s2, 2p6, 3s2, 3p3
Has no paired electrons in 3p orbital.
Each P-electron is in a different orbital.
Sulfur: 1s2, 2s2, 2p6, 3s2, 3p4
Has 2 of its p-electrons paired in a p-orbital.
It will be easier to remove 1 of the electrons due to the repulsion of the other electron in the same orbital.
Less energy needed.
3.2.2 Group 2, The Alkaline Earth Metals
State whether the atomic radius increases or decreases down group 2.
Atomic radius increases, atoms have more shells of electrons making the atom bigger.
3.2.2 Group 2, The Alkaline Earth Metals
State whether the 1st ionisation energy increases or decreases down group 2.
Decreases.
The outer e- are held more weakly because they are further from the nucleus in additional shells, weaker attraction between N and outer E.
Outer shell electrons become more shielded from the attraction of the nucleus by the repulsive forces of the inner shell electrons.
Less energy is needed to remove outer electron.
There is an increase in n.o of protons down the group but the shielding effect overrides an increase in + charge.
