Periods in the Periodic Table
Periods in the Periodic Table
The following diagram illustrates some of the key trends in the periods:
Trends on the periodic table.
The table below summarises the patterns or trends in the properties of the elements in period 3. Similar trends are observed in the other periods of the periodic table. The chlorides are compounds with chlorine and the oxides are compounds with oxygen.
|
Element |
\(_{11}^{23}\text{Na}\) |
\(_{12}^{24}\text{Mg}\) |
\(_{13}^{27}\text{Al}\) |
\(_{14}^{28}\text{Si}\) |
\(_{15}^{31}\text{P}\) |
\(_{16}^{32}\text{S}\) |
\(_{17}^{35}\text{Cl}\) |
|
Chlorides |
\(\text{NaCl}\) |
\(\text{MgCl}_{2}\) |
\(\text{AlCl}_{3}\) |
\(\text{SiCl}_{4}\) |
\(\text{PCl}_{5}\) or \(\text{PCl}_{3}\) |
\(\text{S}_{2}\text{Cl}_{2}\) |
no chlorides |
|
Oxides |
\(\text{Na}_{2}\text{O}\) |
\(\text{MgO}\) |
\(\text{Al}_{2}\text{O}_{3}\) |
\(\text{SiO}_{2}\) |
\(\text{P}_{4}\text{O}_{6}\) or \(\text{P}_{4}\text{O}_{10}\) |
\(\text{SO}_{3}\) or \(\text{SO}_{4}\) |
\(\text{Cl}_{2}\text{O}_{7}\) or \(\text{Cl}_{2}\text{O}\) |
|
Valence electrons |
\(3\text{s}^{1}\) |
\(3\text{s}^{2}\) |
\(3\text{s}^{2}3\text{p}^{1}\) |
\(3\text{s}^{2}3\text{p}^{2}\) |
\(3\text{s}^{2}3\text{p}^{3}\) |
\(3\text{s}^{2}3\text{p}^{4}\) |
\(3\text{s}^{2}3\text{p}^{5}\) |
|
Atomic radius |
Decreases across a period. |
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|
First Ionization energy |
The general trend is an increase across the period. |
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|
Electro-negativity |
Increases across the period. |
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|
Melting and boiling point |
Increases to silicon and then decreases to argon. |
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|
Electrical conductivity |
Increases from sodium to aluminium. Silicon is a semi-conductor. The rest are insulators. |
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Table: Summary of the trends in period 3
Note that we have left argon (\(_{18}^{40}\text{Ar}\)) out. Argon is a noble gas with electron configuration: \([\text{Ne}]3\text{s}^{2}3\text{p}^{6}\). Argon does not form any compounds with oxygen or chlorine.
This lesson is part of:
Classification of Matter