Everything Science Grade 10

5.1 CHAPTER 5. THE PERIODIC TABLE

Element^2311 Na^2412 Mg^2713 Al^2814 Si^3115 P^3216 S^3517 Cl

Chlorides NaCl MgCl 2 AlCl 3 SiCl 4 PCl 5 or

PCl 3

S 2 Cl 2 no chlo-

rides

Oxides Na 2 O MgO Al 2 O 3 SiO 2 P 4 O 6 or

P 4 O 10

SO 3 or

SO 4

Cl 2 O 7 or

Cl 2 O

Valence elec-

trons

3 s^13 s^23 s^23 p^13 s^23 p^23 s^23 p^33 s^23 p^43 s^23 p^5

Atomic

radius

Decreases across a period.

First Ioniza-

tion energy

The general trend is an increase across the period.

Electro-

negativity

Increases across the period.

Melting and

boiling point

Increases to silicon and then decreases to argon.

Electrical

conductivity

Increases from sodium to aluminium. Silicon is a semi-conductor.

The rest are insulators.

Table 5.1: Summary of the trends in period 3

Note that we have left argon (^4018 Ar) out. Argon is a noble gas with electron configuration:
[Ne] 3 s^23 p^6. Argon does not form any compounds with oxygen or chlorine.

Exercise 5 - 1

1. Use Table 5.1 and Figure 5.2 to help you produce a similar table for the

elements in period 2.

2. Refer to the data table below which gives the ionisation energy (in kJ·

mol−^1 ) and atomic number (Z) for a number of elements in the periodic

table:

98 Chemistry: Matter and materials