GCSE OCR Gateway C4:1 d-f The Reactivity Series of Metals (1)

C4:1 d-f The Reactivity Series of Metals (1)

C4.1d To be able to predict possible reactions and probable reactivity of elements from their positions in the Periodic Table.

C4.1e To be able to explain how the reactivity of metals with water or dilute acids is related to the tendency of the metal to form its positive ion including reaction of metals with water, dilute hydrochloric acid and the displacement reactions involving metals and metal salts.

C4.1f To be able to deduce an order of reactivity of metals based on experimental results.

Reactivity of elements and the Periodic Table

a) Non–metals (Groups 5-7)

Non-metals like Halogens oxidize other elements.

Halogens need one electron to fill their outer shell.

Halogens obtain that one electron from other elements or compounds.

So    X₂    +     2 electrons    ⟶    2X^–     where X is one of the halogens.

b) Metals (Groups 1-3)

Metals behave in the opposite way.

Metals reduce other elements and compounds.

Metals lose their outer shell electrons.

This leaves a positive metal ion.

The number of positive charges equal to the number of electrons lost.

So M    ⟶   M⁺     +    1 electron  where M is a metal.

I’ve added the features of metals and non- metals to the Periodic Table below:

As the C4.1d learning objective notes you can tell from the position of an element in the Periodic Table how it will react.

So we can predict that when calcium metal reacts it will probably lose its two outer shell electrons (its in Group 2) reduce other elements or compounds and become a 2+ charged ion.

Ca   ⟶    Ca ²⁺     +    2e–

Or we can predict that when oxygen reacts with another element or compound each oxygen atom probably gains 2 electrons (its in Group 6) and becomes a negatively charged ion.

O₂    +    4e–    ⟶    2O^2–

Metals reacting with water

So how will metals react with water?

We’ve already seen in another post how the alkali (Group 1) metals react with water.

Here is a video that demonstrates those reactions brilliantly.

The metal reduces water to hydrogen and the metal hydroxide, for example:

Sodium   +    water     ⟶    sodium hydroxide     +   hydrogen

Na    +         H₂O        ⟶               NaOH                 +            ½H₂

But how do we “measure” reaction?

As metals reduce water to hydrogen then one way would be to observe the rate of bubbles of hydrogen given off.

Another would be to use a gas syringe to measure the volume of hydrogen given off per minute.

It’s definitely difficult to measure an explosion!!

This video shows how the alkaline earths (Group 2 metals) react with water.

Again the alkaline earth metal reduces water to hydrogen and the metal hydroxide, for example:

calcium   +    water     ⟶    calcium hydroxide     +   hydrogen

Ca     +         2H₂O        ⟶               Ca(OH)₂           +       H₂

From these results, we can see already that there is an order of reactivity:

Most Reactive: Caesium

                           Rubidium

                           Potassium

                           Sodium

                           Lithium

                           Barium

                           Strontium

                           Calcium

Least Reactive   Magnesium

Metals reacting with dilute hydrochloric acid

If Group 1 and group 2 metals react vigorously with water than they react even more vigorously with dilute hydrochloric acid.

This video shows this :

So zinc is less reactive than magnesium.

You can see it fizzing slightly in the above video.

Zinc     +    Hydrochloric acid  ⟶   Zinc chloride    +    hydrogen

Zn       +       2HCl                       ⟶           ZnCl₂              +        H₂

Other metals are less reactive still.

Iron, lead, copper, silver, gold etc.

There position in any reactivity series is measured using metal–metal ion displacement reactions.

I’ll post on metal–metal ion displacement reactions in my next post on the reactivity series.