Inorganic Chem

Question 1

In the periodic table, elements are placed according to ____

Answer 1

increasing atomic number

Question 2

Vertical columns

Answer 2

Groups

Question 3

Horizontal rows

Answer 3

Periods

Question 4

Atomic radius

Answer 4

the distance between the nucleus and the outermost electron of an atom

Question 5

Atomic radius of period 3 (increase or decrease)

Answer 5

decrease

Question 6

Ionic radius

Answer 6

the distance between the nucleus and the outermost electron of an ion

Question 7

Ionic radius of period 3 (increase or decrease)

Answer 7

decrease

Question 8

Why does ionic radius decrease? (2 parts)

Answer 8

From Na^+ to Si^4+, ions get smaller due to the increasing nuclear charge attracting the outer electrons in the second principal quantum shell nucleus (which has an increasing atomic number)

From P^3- to Cl^–, the ionic radii decreases as the nuclear charge increases across the period and less electrons are gained by the atoms (P gains 3 electrons, S 2 electrons and Cl 1 electron)

Question 9

Melting point (from Na to Al) and explain it (3 points)

Answer 9

Increases

1. Na, Mg and Al are metallic elements which form positive ions arranged in a giant lattice in which the ions are held together by a ‘sea’ of delocalised electrons around them
2. Since Na will donate one electron into the ‘sea’ of delocalised electrons, Mg will donate two and Al three, this causes the metallic bonding in Al to be stronger than in Na or Mg
3. This is because the electrostatic forces between a 3+ ion and the larger number of negatively charged delocalised electrons are much larger compared to a 1+ ion and the smaller number of delocalised electrons in Na

Question 10

Melting point from P to Ar

Answer 10

Decrease

1. covalent bonds within the molecules are strong, however, between the molecules, there are only weak instantaneous dipole-induced dipole forces
2. It is easy to break them so the melting points decrease going from P to Ar (note that the melting point of S is higher than that of P as sulphur exists as larger S8 molecules compared to the smaller P4 molecule)

Question 11

Electrical conductivity from Na, Mg, Al

Answer 11

Valence electrons that are donated in sea of electrons increase

so there are more electrons moving around the structure of Al, hence making it a better electrical conductor than Al

Question 12

Electrical conductivity from Si, P, S

Answer 12

Si has a giant molecular structure, so no delocalized electron

P and S also have a lack of delocalized electrons

Question 13

First ionization energy

Answer 13

the energy required to remove one mole of electrons from one mole of atoms of an element in the gaseous state to form one mole of gaseous ions

Question 14

IE1 trend in period 3 & conclusion

Answer 14

General increase

1. The nuclear charge increases
2. The atomic radius decreases
3. There are stronger attractive forces between the nucleus and outer electrons

THEREFORE, it gets harder to remove any electrons