Order metals by ease of forming positive ions using reactivity series.

1. Understand Reactivity and Ion Formation: The reactivity series lists elements in order of their reactivity. Elements higher in the series are more reactive and more easily form positive ions because they tend to lose electrons more readily. The problem asks to order the given metals (Potassium, Sodium, Calcium, Copper, Gold) according to how easily they form positive ions, which means ordering them from most reactive to least reactive.

1. Consult the Reactivity Series: The provided reactivity series is: Potassium, Sodium, Calcium, Magnesium, Aluminium, Carbon, Zinc, Iron, Hydrogen, Copper, Silver, Gold.

1. Identify the Metals in the Series: Locate the metals given in the problem within the reactivity series: Potassium, Sodium, Calcium, Copper, and Gold.

4. Order the Metals by Reactivity: Based on their position in the reactivity series, arrange the metals from highest reactivity (most easily forms positive ions) to lowest reactivity (least easily forms positive ions).
* Potassium is at the top.
* Sodium is next.
* Calcium follows Sodium.
* Copper is much lower down.
* Gold is at the very bottom.

1. List the Metals in Order: Therefore, the order from most easily forming positive ions to least easily forming positive ions is: Potassium, Sodium, Calcium, Copper, Gold.