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==Key Stage 3==
===Meaning===
A [[Period]] '''period''' is a row on the [[Periodic Table]] whose [[element]]s all have the same number of [[Electron Shell]]s.
===About Periods===
: [[Atomic Number]] increases as you move along a [['''period]]'''.
{| class="wikitable"
| style="height:20px; width:300px; text-align:center;" |There is a trend in the [[Melting Point]]s as you move along the [[Period (Chemistry)|period]].
| style="height:20px; width:300px; text-align:center;" |A similar trend can be seen in the next [[Period (Chemistry)|period]].
|}
==Key Stage 4==
===Meaning===
A '''period''' is a row on the [[Periodic Table]] whose [[element]]s all have the same number of [[Electron Shell]]s.
===About Periods===
: [[Atomic Number]] increases as you move along a '''period'''.
: The number of the '''period''' is the same as the number of [[Electron Shell|electron shells]].
====Trends within Periods====
{| class="wikitable"
|-
|[[File:Period2ElectronShells.png|center|600px]]
|-
|[[File:Period2ElectronShielding.png|center|600px]]
|-
| style="height:20px; width:600px; text-align:left;" |For the first 3 [[element]]s [[Lithium]], [[Beryllium]] and [[Boron]] all lose [[electron]]s in [[Chemical Reaction|chemical reactions]].
The [[reactivity]] decreases as you go across the [[Period (Chemistry)|period]] because:
*The outer [[electron]]s are all roughly the same distance away from the [[Atomic Nucleus|nucleus]].
*The [[charge]] on the [[Atomic Nucleus|atomic nucleus]] increases as you move go across the [[period]] but the [[electron]] shielding caused by the two inner [[electron]]s remains the same. This causes the [[electron]]s to experience a greater [[force]] of [[attraction]] as you move along the [[period]], making it harder for the [[atom]]s to lose [[electron]]s and become [[ion]]s.
[[Nitrogen]], [[Oxygen]] and [[Fluorine]] can all gain [[electron]]s to become [[Negative Charge|negative]] [[ion]]s in certain [[Chemical Reaction|reaction]]s.
The [[reactivity]] increases as you go across the [[Period (Chemistry)|period]] because:
*The outer [[electron]]s are all roughly the same distance away from the [[Atomic Nucleus|nucleus]].
*The [[charge]] on the [[Atomic Nucleus|atomic nucleus]] increases as you move go across the [[period]] but the [[electron]] shielding caused by the two inner [[electron]]s remains the same. This causes the [[electron]]s to experience a greater [[force]] of [[attraction]] as you move along the [[period]], making it easier for an [[atom]]s to gain more [[electron]]s to become [[ion]]s.
|}