Periodicity

Question 1

What are the types of compounds in period 3? What properties do they have because of this

Answer 1

• Na, Mg, and Al are metallic
  
  • shiny when freshly exposed to air
  • conduct electricity
  • react w dilute acids to give hydrogen and salts
• silicon is a semi-metal or mettalloid
  
  • conducts electricity to some extent
  • used as a semicondcuctior
• P, S, and Cl, are typical non-metal
  
  • do not conduct
  • low melting and boiling pitsn
• argon is a noble gas
  
  • chemically unreactive
  • exuists as separate reaction

Question 2

Which period 3 elements react with water ?

Answer 2

• Sodium and magnesium
• and chlorine

Question 3

What happens when sodium is placed in water?

Answer 3

• NaOH and H2 is evolved
• vigorous reaction
• sodium floats on surface and fizzes rapidly, leting because of the heat released by the reaction
• strongly alkaline soln formed

Question 4

WHat is the equation for the reaction and observations when Magnesium is palced in water

Answer 4

• Mg + H2O → Mg(OH)2 + H2O
• slow, few bubbles
• less alkaline, sparingly soluble

Question 5

What happens when heated magnesium reacts with steam?

Answer 5

• reaction is much faster
• gives MgO and hydrogen gas

Question 6

What happens when sodium is burnt in oxygen?

Answer 6

• Na2O released
  
  • as oxygen has a oxd state of -2 and Na is +1
• burns brightly with yellow flame
• forms white sodium oxide

Question 7

WHat is the equation and obsevations for when magnesium is burnt in oxygen:

Answer 7

• bright white flame
• white solid
• 2Mg + O2 → 2MgO

Question 8

What happens when aluminium is burnt in oxygen?

Answer 8

• aluminium poder heated burns brightly in air
• gives aluminium oxide
  
  • Al2O3
• aluminium becomes coated with the surface layer of oxide strongly bonded due to rapid reaction

Question 9

What happens when silicon is burnt in oxygen?

Answer 9

• form oxide when strongly heated in oxygen
• SiO2

Question 10

What happens when phosphorus is burnt in oxygen?

Answer 10

• red phosphorus
  
  • must be heated before it will react
• white phosphorus
  
  • spontaneous ignites in air and the white smoke of phosphorus pentoxide is given off
• red and white phosphorus are allotropes, same element with the atoms arranged differently
• P₄O₁₀ released
• if oxygen supply is limited, phosphorus trioxide is form, P₂O₃

Question 11

What happens when sulfur is burn in oxygen?

Answer 11

• burns with blue flame
• forms the colourless gas sulfur dioxide and a little sulfur trioxide forms

Question 12

What type of reaction is it with period 3 elements and oxygen?

Answer 12

• redox
• oxygen oxidised to -2
• period 3 element reduced