Metals and Non-Metals Formula and Equations

Our Earth contains more than hundred elements till and simplest classification of elements till now is basis on whether an element is metal or non-metal. 

Keyterms: Metal, Non-metal, Element, Mercury, Lithium, Potassium, Gallium, Caesium, Alkali, s-block

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What are Metals and what are their properties?

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Basically, Metals comprises of those elements that are generally in solid state (except Mercury which is liquid at room temperature) and possess following physical properties:

• Very Hard (except Alkali metals found in s-block such as Lithium, Potassium, etc.)
• High Melting and Boiling points (except Gallium & Caesium which have very low melting point) 
• Lustrous 
• Malleable
• Ductile
• Excellent conductors of heat and electricity

Most important chemical property is that metals usually form electropositive ions during reactions and therefore, acts as reducing agents.

For e.g., Sodium, Potassium, Calcium, Magnesium, etc.

Chemical Reactions of Metals

Metals are known to be highly electropositive in nature and hence, lose electrons very easily during reactions that makes them reactive. 

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What are Non-Metals and what are their properties?

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Non-Metals are usually in solid and gaseous form (except Bromine which is liquid) and possess following physical properties:

• Brittle
• Soft in nature (except Diamond which is an allotrope of Carbon and is hardest substance on Earth)
• Insulators or poor conductors of heat and electricity (except Graphite which is an allotrope of Carbon and very good conductor)
• Amorphous 
• Non-malleable and non-ductile
• Low melting and boiling points (except Diamond which is an allotrope of Carbon and has very high melting and boiling point)

Most important chemical property is that Non-Metals usually forms electronegative ions during reactions and therefore, acts as an oxidizing agent. 

For e.g., Carbon, Sulphur, Hydrogen, Phosphorous, etc. 

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Why metals are electropositive?

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Let us look at the table mentioning atomic properties of some metals below to find an answer:

By analyzing this table, we can clearly see metals are not stable as they don’t contain 8 electrons in last orbital to complete octet and become stable. We can see 1 or 2 or at last 3 electrons in last orbital of every metal. We know reactions happen by elements to make themselves more stable and stability is defined by OCTET RULE till now what we have studied. So, to obtain octet in their last orbital, they have to either lose electrons or obtain electrons. But, losing is far better than gaining as they need more than 4 electrons whereas metals can lose at most electrons. So, this is the reason why metals lose their electron as it saves their energy to become stable and therefore, making them electropositive during reactions.

Now, we know that why metals are electropositive and reactive, we will see reactions with various reagents:

1. Reaction of metals with air:

Metals are reactive in nature and therefore, forms oxides when exposed to air. Some metals such as Sodium and Potassium even burns in air forming oxides. While other metals form oxide layer that prevents the metal from further oxidation. Copper does not burn, but the hot metal is coated with a black coloured layer of Copper(II) oxide. Even at high temperatures, Silver and gold do not react with oxygen.

Metal + Oxygen = Metal Oxide

For e.g.

When Sodium [Na] reacts with oxygen, it forms Sodium Peroxide in general form. 

2Na + O₂ → Na₂O₂

When Copper [Cu(II)] reacts with oxygen, it forms Copper(II) oxide.

2Cu + O₂ → 2CuO

Metal oxides are basic in nature and mostly insoluble in water but some soluble oxides react with water to form hydroxides (aqueous solution). There are amphoteric oxides too which can react with acid as well as base to such as Zinc oxide and Aluminum oxide.

Aluminum oxide reacts with Sodium Hydroxide to form Sodium Aluminate and water. 

Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O

Aluminum oxide reacts with Hydrochloric acid to form Aluminum Chloride and water.

Al₂O₃ + 6HCl → 2AlCl₃ + H₂O

2. Reaction with metals with water:

Hydrogen gas is liberated when Metals reacts with water and form hydroxides.

For e.g. 

Calcium forms Calcium Hydroxide and Hydrogen by reacting with water.

Ca + 2H₂O → Ca(OH)₂ + H₂

3. Reaction of metals towards dihydrogen:

Metal Hydrides are formed when Metals reacts with dihydrogen.

For e.g. 

Alkali metals react in following way: 

2M + H₂ → 2M⁺H^-

4. Reaction of metals with Halogens:

Metals react with halogens to form halides which are ionic compounds.

For e.g. 

Sodium reacts with Chlorine to form Sodium Chloride.

2Na + Cl₂ → 2NaCl

5. Reaction of metals with acids:

Metals react with dilute acids to form metal salt and liberates hydrogen. But, in case of Nitric acid, even liberated hydrogen is oxidized to water due to strong oxidizing nature of Nitric acid. But exceptions are always there as Manganese and Magnesium only liberates hydrogen when reacted with dilute Nitric acid.

For e.g.

Sodium reacts with dilute Sulphuric acid to form Sodium Sulphate and Hydrogen gas.

2Na(s) + H₂SO₄ (aq) → Na₂SO₄ (aq) + H₂ (g)

6. Reactions of metals with another metal salts:

Metals react with other metal salts according to reactivity series which is mentioned below:

Through this table, we can see that less reactive metals get replaced by high reactive metals in reaction. 

Metal A + Salt Solution of Metal B = Salt solution of Metal A + Metal B

For e.g. 

Iron is more electropositive than Copper and therefore, replace it in this reaction to form Iron Sulphate.

Fe + CuSO₄ → FeSO4 + Cu

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Why non-metals are electronegative?

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Let us look at the table mentioning atomic properties of some non-metals below to find an answer:

By analyzing above table, we can clearly see that non-metals require electrons to achieve stability and complete octet as losing 5 or more electrons will involve more energy than gaining just 1 to 3 electrons during reactions and therefore, non-metals act as electronegative ions during reactions. 

But non-metals show very diverse behavior and therefore, their reactions are different too.

1. Reaction of non-metals with air:

Non-metals reacts with oxygen to form acidic oxides. 

For e.g.

Carbon reacts with oxygen to form Carbon Dioxide.

C + O₂ → CO₂

Phosphorous reacts with Oxygen to form Phosphorous Pentoxide.

P₄ + 5O₂ → 2P₂O₅

2. Reaction of non-metals with water:

Non-metals never reacts with water as they form electronegative and cannot form oxides as well as hydroxides and even reaction cannot be done at higher temperatures.

3. Reaction of non-metals with dihydrogen:

Since, hydrogen is itself a non-metal and therefore, they form covalent bonds and hence, hydrides.

For e.g.

Nitrogen and Hydrogen combines to form most important chemical Ammonia.

N₂ + 3H₂ → 2NH₃ 

4. Reaction of non-metals with halogen:

Non-metals form covalent bond with halogens to form halides. There are various compounds for same halogen as different non-metals possess different electronegativity. These halides undergo hydrolysis too.

For e.g.

Phosphorous reacts with Chlorine to form Phosphorous Trichloride and Phosphorous Pentachloride.

P₄ + 6Cl₂ → 4PCl₃

P₄ + 10Cl₂ → 4PCl₅

5. Reaction of non-metals with acids:

Non-metals don’t react with dilute acids as they cannot replace hydrogen ion and cannot liberate dihydrogen gas.

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Ionic Compounds

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Now, we know that metals form electropositive ions and non-metals form electronegative ions and therefore, when metal and non-metal react, generally ionic compounds formed.

Metals behaves as oxidizing agents and non-metals as reducing agents to form ionic compounds.

For e.g. 

Zn + S → Zn²⁺ + S^2- (ZnS)

2Mg + Cl₂ → 2Mg²⁺ + 2Cl^- (MgCl₂)

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Occurrence of metals

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Metals are most important elements but since, they are highly reactive and forms salts. Extracting metals back to pure form is not an easy task and therefore requires knowledge of metallurgical concepts.

There are various metals and extraction techniques that is shown in figure.

We can see that highly reactive metals need electrolytic process and medium reactivity metals needs carbon reduction technique to extract pure metal. Since, Gold and Silver are least reactive metals and therefore, they are found as pure metals only in ores too.

Reactions that involve extraction of metals are written as follows:

For Mercury:

2HgS (s) + 3O₂ (g) (heated) → 2HgO (s) + 2SO₂ (g)

2HgO (l) (heated) → 2Hg (l) + O₂ (g)

For Manganese:

3MnO₂ (s) + 4Al (s) → 3Mn (l) + 2Al₂O₃ 

For extraction through electrolysis, setup is required as shown in figure. 

This is also known as Hall-Heroult process. Reaction for Aluminum extraction which is done at cathode is shown below:

Cathode reaction: Al³⁺ (melt) + 3^e- → Al (l)

Anode reaction: C + 1/2O^2- → CO/CO₂ + 2/4^e-