Periodicity
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How does the atomic radius change across each period?
decreases - nuclear charge increases pulling electrons in closer - similar sheilding across no so additional shells to screen outer electrons - atom becomes constricted
period 3 Na,Mg,Al bonding structure, forces , melting points
• bonding structure - Giant metallic lattice – positive metal ions surrounded by a sea of delocalised electrons • forces - Strong electrostatic forces between the positive metal ion and delocalised electrons. • melting points - high melting points - increasing across group
period 3 Si bonding structure, forces , melting points
• bonding structure - Giant covalent Macromolecular • forces - Many strong covalent bonds – lots of energy required to overcome these • melting points - highest melting point
period 3 P bonding structure, forces , melting points
• bonding structure - P4 , Simple molecular • forces - Weak intermolecular forces – Van der Waals forces • melting points - low melting point
period 3 S bonding structure, forces , melting points
• bonding structure - S8 , Simple molecular • forces - Weak intermolecular forces – Van der Waals forces stronger than for P as larger molecule • melting points - low melting point
period 3 Cl bonding structure, forces, melting points
• bonding structure- Cl2 Simple molecular • forces - Weak intermolecular forces – Van der Waals forces -Smaller than P so weaker forces • melting points - lowest
period 3 Ar bonding structure, forces, melting points
• bonding structure- atomic • forces- Very weak forces between the atoms • melting points - lowest
period 3 trends in melting points
• increases due to the more delocalised electrons present and greater nuclear charge from Na,Mg,Al • si forms giant covalent lattices with many strong covalent bonds • dcreases for the rest as they are allsimple molecular with weak VDW forces • Al deviates so does S
period 3 Why does Al deviate
The outer electron is being removed from a 3p orbital * The 3p orbital is further away from the nucleus than the 3s orbital
period 3 Why does sulphur deviate ?
• Sulfur has a 3p orbital containing two electrons • The spin repulsion between them decreases the energy required to remove one of them
period 3 Conductivity of period 3
• Al,Mg,Na - all good conductors due to metalic structure • Si - semi-conduuctor • the rest do not conduct because they are simple molecules - no free electrons or ions
period 3 What is the equation and observation for when Sodium reacts with WATER?
2Na + H2O ——> 2NaOH + H2 Effervescence AND Floats
period 3 What is the equation and observation for when Magnesium reacts with COLD WATER?
Mg + 2H2O(l) ——> Mg(OH)2 + H2 White ppt
period 3 What is the equation and observation for when Magnesium reacts with gaseous WATER?
Mg + H2O(g) ——> MgO + H2O White Solid AND Bright White Light
period 3 What is the equation and observation for when Chlorine reacts with WATER? (Without UV)
Cl2 + H2O <===> HCl + HClO “Disproportionation”
period 3 What is the equation and observation for when Sodium reacts with OXYGEN?
4Na + O2 ——> 2Na2O Yellow Flame AND White Solid
What is the equation and observation for when Magnesium reacts with OXYGEN?
2Mg + O2 ——> 2MgO Bright White Flame AND White Solid
period 3 What is the equation and observation for when Aluminium reacts with OXYGEN?
4Al + 3O2 ——> 2Al2O3 Bright White Flame AND White Solid
period 3 What is the equation and observation for when Silicon reacts with OXYGEN?
Si + O2 ——> SiO2 White Flame AND White Solid
period 3 What is the equation and observation for when Phosphorus reacts with OXYGEN?
P4 + 5O2 ——> P4O10 Very Bright White Flame AND White Solid