Periodicity -Grp 2,3,7

• What is periodicity?

  repeating patterns in the properties of elements across each period
• What is the structure of Na,Mg and Al?

  Giant metallic lattice
• What is the structure of silicon?

  Giant covalent lattice
• What is the structure of P,S and Cl?

  Simple molecular
• What happens to the melting and boiling point as you go from sodium to aluminium across the group?

  increases
• Why does melting and boiling point increase from sodium to aluminium in period 3?

  charge on the ion increases and more delocalised electrons so more energy needed to break the stronger metallic bonding
• List the 3 simple molecules in period 3 in terms of descending melting and boiling point ( starting with the highest first)?

  sulfur

  phosphorus

  chlorine
• What molecule does sulfur exist as?

  S8
• What molecule does phosphorus exist as?

  P4
• What molecule does chlorine exist as?

  Cl2
• Why does sulfar have a higher melting point than chlorine and phosphorus?

  stronger Van der waals due to more electrons and larger structure
• Which element has the highest melting point in period 3?

  silicon
• Why does silicon have a high melting point?

  Giant covalent lattice so lot's of strong covalent bonds and no weak intermolecular forces so alot of energy needed to break strong bonds
• What happens to the atomic radius as you go across a period?

  Decreases
• Why does atomic radius decrease across a period?

  greater nuclear charge so electrons are pulled closer to nucleus and atoms experience same amount of shielding
• What happens to atomic radius as you go down a group?

  Increases
• Why does atomic radius increase down a group?

  greater number of shells and more shielding
• What is the formula for the product when phosphorus reacts with oxygen?

  P4O10
• What are the 2 types of sulfurs formed when sulfur reacts with oxygen?

  Sulfur dioxide and sulfur trioxide
• When oxygen reacts with sodium describe the appearance of product formed?

  white powder
• Why does sodium oxide ( white powder) have a yellow tint?

  sodium oxidised into sodium peroxide
• What flame does sodium burn with in oxygen?

  yellow
• What flame does magnesium burn with in oxygen?

  white flame
• Describe what magnesium oxide looks like when produced?

  white powder
• What colour flame does aluminium burn with in oxygen?

  white flame
• At high temperatures when aluminium reacts with oxygen describe what aluminium oxide looks like?

  white powder
• What are the 2 allotropes of phosphorus?

  white phosphorus and red phosphorus
• When white phosphorus reacts with oxygen describe what the products looks like?

  white solid with white smoke
• Give the formula of the oxide of phosphorus formed when oxygen is in short supply?

  P4O6
• What colour flame does Sulfur burn with in oxygen?

  blue
• Write the formula for Phosphoric acid?

  H3PO4
• Write the formula for sulfurous acid?

  H2SO3
• Write the formula for sulfuric acid?

  H2SO4
• Which of the Period 3 elements react with cold or room temperature water?

  Sodium

  Magnesium

  Chlorine
• What are the products formed when magnesium reacts with steam?

  Magnesium oxide and hydrogen gas
• Why does magnesium hydroxide form a much less alkaline solution than sodium hydroxide?

  less soluble
• Explain how the covalent character of aluminium oxide arises.?

  The aluminium cation is very small

  
  

  This means that the aluminium cation is closer to the oxide ion

  
  

  The cation is also highly charged enough to distort the electron cloud

  
  

  Therefore, the electron cloud appears more covalent
• What is the approximate pH of Mg(OH)2?

  10
• What is the approximate pH of H3PO4?

  1-2
• What is the approximate pH of H2SO4?

  0-1