Periodicity of the period 3 elements
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- Created by: Izzy Wood
- Created on: 08-02-14 12:39
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- Periodicity of period 3 elements
- About the Elements
- Phosphorus - P4 (15)
- Bonds broken - Van der Waals' forces
- Bonding - Simple molecular
- Silicon - Si (14)
- Bonds broken - Covalent
- Bonding - Giant covalent
- Sulphur - S8 (16)
- Bonding - Simple molecular
- Bonds broken - Van der Waals' forces
- Chlorine - Cl2 (17)
- Bonds broken - Van der Waals' forces
- Bonding - Simple molecular
- Magnesium - Mg (12)
- Bonds broken - Metallic
- Bonding - Metallic bonding
- Argon - Ar (18)
- Bonds broken - Van der Waals' forces
- Bonding - Monatomic
- Sodium - Na (11)
- Bonding - Metallic bonding
- Bonds broken - Metallic
- Aluminium - Al (13)
- Bonds broken - Metallic
- Bonding - Metallic bonding
- Phosphorus - P4 (15)
- General trends across the elements
- Atomic radius decreases as the atomic number increases, this is because the nuclear charge increase (due to the increase in protons pulling the electrons).
- First ionization energy increases as the atomic number increases, as the nuclear charge increases.
- Exceptions include Aluminium and Sulphur. Sulphur dips because phosphorus has 3 electrons in its outer sublevel, while sulphur has 4, but there are 3 orbitals so 2 electrons share an orbital. These repel due to mutual repulsion.
- Melting and boiling point increases through the period up to silicon where it begins to decrease all the way to Argon. This is because the bonds being broken are becoming weaker down the period.
- Reactions of Period 3 elements with water
- Magnesium
- It reacts very slowly with water to produce magnesium hydroxide and hydrogen.
- Mg + 2H2O > Mg(OH)2 + H2
- Magnesium does react vigorously with steam to produce magnesium oxide.
- Sodium
- Reacts vigorously with water to form Sodium hydroxide and Hydrogen.
- 2Na + 2H2O > 2NaOH +H2
- pH of resulting solution of NaOH is 12-14.
- Aluminium and silicon are both protected from reacting with water by a thin layer of their oxides.
- Phosphorus, Sulphur and Argon do not react with water.
- Chlorine
- Reacts with water to form a mixture of hydrochloric acid and chloric(I) acid.
- Cl2 + H20 > HCl + HClO
- Magnesium
- Reactions of period 3 elements with oxygen
- Chlorine and argon do not react with oxygen.
- Sulphur
- It burns readily in air with a blue flame, producing choking SO2.
- Sodium
- Reacts vigorously in air or oxygen with a yellow flame. White Na2O is produced.
- Phosphorus
- White phosphorus ignites spontaneously in air. Burning with a bright light and producing with phosphorus (V) oxide.
- Magnesium
- Burns very vigorously in air or oxygen with a brilliant white flame. Whit MgO is produced.
- Silicon
- Silicon is also protected by a thin layer of its oxide and resists attack by oxygen at temps up to 900C, forming SiO2.
- Aluminium
- Aluminium reacts with oxygen to form a thin layer of Al2O3, meaning pieces of aluminium do not burn in air. But powdered aluminium burns vigorously.
- Physical properties of the period 3 oxides.
- Melting points of the period 3 oxides increase from Na2O to MgO and then decrease steadily.
- Sodium, magnesium and aluminium oxides have the highest melting points, and exist as giant ionic lattices. Very many strong ionic bonds must be overcome for these to melt,
- Silicon(IV) oxide has a giant covalent structure. It has very many covalent bonds that must be broken to melt it. Giving it a high melting point.
- Sulphur(VI) oxide exists as rings of three molecules so the Van der Waals' forces are weaker between the molecules. It's liquid at room temp.
- Phosphorus(V) oxide exists as simple covalent molecules but has a large relative formula mass, so the Van der Waals' forces are strong.
- Electrical conductivity
- The ionic compounds conduct when molten. So sodium oxide, magnesium oxide and aluminium oxide conduct when molten.
- Covalent molecules do not conduct electricity. But P4O10 and SO3 do react with water forming acidic solutions which can conduct.
- Melting points of the period 3 oxides increase from Na2O to MgO and then decrease steadily.
- Period 3 oxides reacting with water
- Magnesium oxide is only slightly soluble in water, the pH of resulting solution being 10.
- MgO + H2O > Mg(OH)2
- Aluminium oxide and silica are insoluble in water.
- Sodium oxide reacts exothermically with water, with a pH of resulting solution being 14.
- Na2O + H2O > 2NaOH
- Phosphorus oxide reacts vigorously with water in a very exothermic reaction, the pH of the resulting solution being 0.
- P4O10 + 6H2O > 4H3PO4
- Sulphur(IV) oxide dissolves readily in water and reacts with it to form sulphuric(IV) acid, with a pH of 1. Sulphur(VI) oxide reacts with water and forms sulphuric acid with a pH of 0.
- SO2 + H2O > H2SO3
- SO3 + H2O > H2SO4
- Magnesium oxide is only slightly soluble in water, the pH of resulting solution being 10.
- About the Elements
- Aluminium - Al (13)
- Bonds broken - Metallic
- Bonding - Metallic bonding
- Reactions of period 3 elements with oxygen
- Chlorine and argon do not react with oxygen.
- Sulphur
- It burns readily in air with a blue flame, producing choking SO2.
- Sodium
- Reacts vigorously in air or oxygen with a yellow flame. White Na2O is produced.
- Phosphorus
- White phosphorus ignites spontaneously in air. Burning with a bright light and producing with phosphorus (V) oxide.
- Magnesium
- Burns very vigorously in air or oxygen with a brilliant white flame. Whit MgO is produced.
- Silicon
- Silicon is also protected by a thin layer of its oxide and resists attack by oxygen at temps up to 900C, forming SiO2.
- Aluminium
- Aluminium reacts with oxygen to form a thin layer of Al2O3, meaning pieces of aluminium do not burn in air. But powdered aluminium burns vigorously.
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