Unit 2: Section 3 - Period 3 elements Flashcards
What is the appearance and what are the physical properties of sodium?
- Metallic
- Shiny
- Conducts electricity (worst conductor of the metals)
Reaction of sodium with acid?
Na + acid -> H2 + salt
Reaction of sodium with cold water - equations and observations?
Vigorous reaction, floats on water, fizzes, melts due to -ΔH of the reaction
NaOH is pH 13-14
2Na + 2H2O -> 2NaOH + H2
Reaction of sodiuma with oxygen (equations and observations)?
2Na + 1/2O2 -> Na2O
Bright yellow flame, forms white powder of Na2O
Appearance and physical properties of magnesium
Metallic, shiny, conducts electricity (between Na and Al in terms of how well it does)
Reaction of Mg with cold water (observations and equation)?
Very slow reaction ph=10 as (Mg(OH)2 is sparingly soluble
Mg + 2H2O -> H2 + Mg(OH)2
Reaction of Mg with steam (observations and equation)?
Much faster than with cold water
Mg + H2O -> MgO + H2
Reaction of Mg with oxygen (observations and equation)?
Bright white flame, forms white powder of MgO
2Mg + O2 -> 2MgO
Appearance and physical properties of alumnium
Metallic, shiny, best conductor of electricity in period 3
Reaction of Al with cold water
No reaction
Reaction of Al with oxygen (equation and observations)?
Heat and lower into jar of O2 -> bright flame, forms white powder
4Al + 3O2 -> 2Al2O3
Why is aluminium considered unreactive even though the metal itself is reactive?
- Covered by Al2O3 from where oxygen has oxidised the surface of Al
- Al2O3 is unreactive
- Makes it sueful for saucepans, window frames
- If Al2O3 is scratched off, Al reacts rapidly with air to form a new coat
Appearance and physical properties of silicon?
Semimetal (metalloid), semiconductor (conducts electrcity to an extent in certain conditions)
Reactions of silicon with oxygen (observations and equation)?
Heat strongly
Si + O2 -> SiO2 (white powder)
Appearance and physical properties of phosphorus?
- Non-metal, low m.p. and b.p. does not conduct electricity
- Red phosphorus as a crystal structure
- White phosphorus as P4
Reaction of phosphorous in excess oxygen (observations and equation)?
Red P needs to be heated significantly first, white P ignites spontaneously in air
Phosphorus pentoxide (white crystalline solid) formed
4P + 5O2 -> P4O10
Reaction of phosphorus in limited oxygen (observations and equation)?
Incomplete combustion: colourless liquid phosphorus trioxide is formed
4P + 3O2 -> p4O6
Appearance and physical properties of sulfur?
Non metal, low mp and bp, does not conduct electricity
Reaction of sulfur with oxygen (observations and equation)?
- Need to heat and lower into a jar of oxygen
- Colourless gas sulfur dioxide formed
- Some SO3 also formed
- S + O2 -> SO2
What are the different types of structure and bonding displayed by the period 3 oxides?
- Na ionic lattice
- Mg ionic lattice
- Al ionic lattice with covalent character; Al3+ distorts O2- electron cloud
- Si giant covalent
- P simple molecular covalent
- S simple molecular covalent
What is the trend in melting points for period 3 oxides (state highest and lowest and why and)?
Highest - MgO Lowest - SO2
Increases along group for metals for Na2O and MgO due to stronger ionic bonding, but Al2O3 is lower due to the covalent character of the bonding
Decreases with size for simple molecular molecules
Which period 3 oxides are basic?
Na2O and MgO
Reaction of Na oxide with water? pH?
Na2O + H2O -> 2Na+ + 2OH-
pH = 14
Reaction of Mg oxide with water? pH?
MgO + H2O -> Mg^2+ + 2OH- ⇌ Mg(OH)2
pH = 9-10 as Mg(OH)2 is sparingly soluble
