Quick questions on Metal reactivity series and displacement reactions: VCE Chemistry Unit 2

Metals can be ranked by how readily they lose electrons (how readily they are oxidised). The more readily they lose electrons, the more reactive they are. A workable VCE-level order, most reactive first:

A metal displacement reaction is one where a metal in elemental form reduces the cation of a less reactive metal, taking its place in solution:

The most reactive metals (group 1 and the more reactive group 2) react directly with cold water to produce hydrogen gas and a metal hydroxide:

Any metal above hydrogen in the activity series reacts with a dilute acid (such as $HCl$ or dilute $H_2SO_4$) to give hydrogen gas and a soluble salt:

All but the noble metals react with oxygen, though the rate and the temperature required differ enormously.

A metal that is high in the activity series is also reactive with water, with dilute acid and with oxygen, and is a strong displacer of less reactive metals. A metal at the bottom is unreactive with all three and cannot displace any other metal in solution.

Always check: is the elemental metal above or below the metal in the salt? If below, the answer is "no reaction" and that is the full answer (no equation needed).

Iron forms both $Fe^{2+}$ and $Fe^{3+}$; the typical product of a simple displacement is $Fe^{2+}$. Copper forms $Cu^+$ and $Cu^{2+}$; the standard form in solution is $Cu^{2+}$.

The anion of the salt ($SO_4^{2-}$, $NO_3^-$, $Cl^-$) is always a spectator and is not shown.

A reactive metal is a strong reductant (gives up electrons easily). Electronegativity describes a covalent bonding partner's attraction for shared electrons. Sodium is very reactive (low electronegativity 0.93); fluorine is highly electronegative (3.98) and is itself reactive but on the oxidising side, not the metal side.

They are reactive, not unstable. They are stable in their unreactive state under oil; the explosive behaviour is the rapid reaction with water releasing hydrogen which ignites.