chemical properties of period 3 elements Flashcards
what is sand made out of?
silicon dioxide
what are the oxidation states for this reaction
2Na(s) + 2H2O (l) ~> 2NaOH(aq) + H2 (g)
oxidation state of sodium Na— 0
oxidation state of hydrogen H2O — 1
oxidation state of oxygen H2O — -2
oxidation state of sodium NaOH — 1
oxidation state of hydrogen NaOH — 1
oxidation state of oxygen NaOH — -2
oxidation state of hydrogen H2 — 0
redox reaction
what type of solution does sodium hydroxide produce?
alkaline aqueous solution
what type of pH does
1 mol Na2O + 1dm^3 H2O
13-14 pH
what type of solution does magnesium hydroxide form?
alkaline 9-10 pH
less soluble than sodium hydroxide
slower reaction
what does mg and H2O form?
Mg(s) + 2H2O (l) ~> Mg(OH)2 (aq) + H2 (g)
what does mg and steam form?
Mg (s) + H2O (g) ~> MgO (s) + H2 (g)
which of the period 3 elements react with cold or room temperature water?
sodium
magnesium
chlorine
which of the period 3 reactions with water undergo a redox reaction?
sodium and cold water
magnesium and cold water
magnesium and steam
what happens when oxygen reacts with sodium ?
burns with bright yellow flame
forming a white powder sodium oxide
Equation for oxidised sodium
4Na(s) + O2 (g) ~> 2Na2O(s)
what happens when magnesium reacts with oxygen?
Burns with a white flame
is oxidised
MgO is formed
what is the equation of the reaction between aluminium and oxygen?
4Al (s) + 3O2 (g) ~> 2Al2O3 (s)
what does aluminium form when reacted at high temperatures with oxygen?
aluminium oxide thin layer - aluminium foil
white powder
burns with white flame
what is the question when silicon reacts with oxygen?
Si(s) + O2 (g) ~> SiO2 (s)
what does phosphorus have if it’s atoms can be arranged differently?
2 allotropes
what are the two allotropes of phosphorus?
white phosphorus
red phosphorus
what happens when white phosphorus makes contact with oxygen at room temperature?
it spontaneously ignited
vigorous reaction
does red phosphorus react with oxygen at room temperature?
no
needs to be heated up before oxidation
produces white solid and white smoke like white phosphorus
what is the equation of phosphorus with oxygen?
4P(s) + 5O2 (g) ~> P4O10 (s)
what does sulfur form when heated and in contact with oxygen?
burns with blue flame
what is the highest formula of oxide?
SO3
what is the lowest formula of sulfur?
SO2
what is the most obvious physical trend in the period 3 elements is from metals on the left to non-metals on the right?
-sodium, magnesium, and aluminium
metallic
they are shiny (when freshly exposed to air)
conduct electricity and react with dilute acids to give hydrogen and salts
- silicon
semi- metal (metalloid)
conducts electricity to some extent
a property that is useful in making semiconductor devices
-phosphorus,sulfur and chlorine
non metals
do not conduct electricity
low melting and boiling points
-argon
noble gas
unreactive
exists as separate atoms
what type of reactions are the period 3 elements involved in?
oxidation?
redox?
reduction?
all redox reactions
since every element starts with an oxidation state of zero
after it has reacted it ends up with a positive or negative oxidation state
which elements are the only ones which react with cold water?
metals:
sodium
magnesium
all those reactions are redox ones, in which the oxidation state of the metal increases and that of some of the hydrogen atoms decreases
non metals:
chlorine
what does the reaction of sodium with water look like?
vigorous
sodium floats on the surface of the water and fizzes rapidly, melting because of the heat energy released by the reaction
what are the products of the reaction between sodium and water?
strongly alkaline solution of sodium hydroxide
(pH 13-14)
what’s is the equation and oxidation states for the reaction between sodium and water?
2Na (s) + 2H2O (l) ~> 2NaOH(aq) + H2(g)
0. +1. -2. +1. -2 +1. 0
what does the reaction between magnesium and water?
very slow at room temperature
only a few bubbles of hydrogen are formed after some days
what are the products of the reaction between magnesium and water?
solution is less alkaline than in the case of sodium because magnesium hydroxide is sparingly soluble
(pH around 10)
what is the equation and oxidation state of the reaction between magnesium and water?
Mg(s) + H2O(g) ~> MgO(s) + H2 (g)
0. +1.-2. +2. -2. 0
how can you make the reaction between water and magnesium quicker?
the reaction is much faster with heated magnesium and steam
what is the products of heated magnesium and steam?
magnesium oxide and hydrogen
what is the equation and oxidation states heated magnesium and steam?
Mg(s) + H2O(g) ~> MgO(s) + H2 (g)
0. +1. -2. +2. -2. 0
which elects in period 3 react with oxygen?
all elements are relatively reacting
(except for argon)
reactions are exothermic
what happens when sodium reacts with oxygen?
burn brightly in air
yellow flame
forms white sodium oxide
what is the equation and oxidation states for sodium and oxygen?
2Na(s) +1/2 O2 (g) ~> Na2O(s)
0. 0. +1. -2
what happens when magnesium reacts with oxygen?
a strip of magnesium ribbon burns in air with a bright white flame
white powder - magnesium oxide
if burning magnesium is lowered into a gas jar of oxygen the flame is even more intense
what is the equation and oxidation states of the reaction between magnesium and oxygen?
2Mg(s) + O2(g). ~> 2MgO(s)
0. 0. +2. -2
magnesium oxidised
oxygen reduced
what happens when aluminium and oxygen react?
when aluminium powder is heated and then lowered into a gas jar of oxygen, it burns brightly to give aluminium oxide - a white powder
aluminium powder can also burn brightly in air
what is the equation and oxidation states of the reaction between aluminium and oxygen?
4Al(s) + 3O2(g) ~> 2Al2O3(s)
0. 0. +3. -2.
what protects aluminium from reacting further?
it is always coated with a strongly bonded surface layer of oxide
if the surface is scratched, the exposed aluminium reacts rapidly with the air and seals off the surface
what is the equation and oxidation states of silicon and oxygen if it is heated strongly?
Si(s) + O2(g). ~>. SiO2(s)
0. 0. +4. -2
what needs to happen to red phosphorus before it reacts with oxygen?
it needs to be heated
how does white phosphorus react with oxygen?
ignites in air
white smoke of phosphorus pentoxide is given off
what are allotropes?
the same element with the atoms arranged differently
what happens if the supply of oxygen is limited when reacting with phosphorus?
P2O3 is formed
what is the equation and oxidation states of the reaction between phosphorus and oxygen?
4P(s) + 5O2(g). ~> P4O10(s)
0. 0. +5. -2
what happens when sulfur reacts with oxygen?
when sulfureux oxygen powder is heated and lowered into a gas jar of oxygen, it burns with a blue flame to form
colourless gas sulfur dioxide
little sulfur trioxide
what happens when sulfur reacts with oxygen?
when sulfureux oxygen powder is heated and lowered into a gas jar of oxygen, it burns with a blue flame to form
colourless gas sulfur dioxide
little sulfur trioxide
what is the equation and oxidation states of the reaction between sulfur and oxygen?
S(s) + O2 (g) ~> SO2(g)
0. 0. +4 -2
what happens to the oxidation state of the period 3 elements as you move from left to right across the period?
the oxidation number in the oxide increases
what are the trends in the physical properties of the period 3 compounds a result of?
the change from metal elements on the left of the periodic table to non metal elements on the right
the oxides are representative of these trends
what are sodium, magnesium and aluminium oxides examples of?
compounds formed by a metal combined to a non metal
they form giant ionic lattices where the bonding extends through the compound
resulting in high melting points
what is the bonding in aluminium oxide?
ionic but has some covalent character
-aluminium forms a very small ion with a large positive charge and so can approach closely O2- and distort its electron cloud
so the bond also has some added covalent character
how can you predict the ionic character of a bond?
by considering the difference in electronegativities between the two atoms
the bigger the difference
the greater the ionic character of the bond
a bond between two identical atoms (such as in oxygen) must be 100% covalent
what type of structure does silicon oxide have?
covalent
macromolecular structure
the bonding extends throughout the giant structure
high melting point because many strong covalent bonds must be broken to melt it
Which molecules exist as separate covalently bonded molecules?
Phosphorus and sulfur oxides
Phosphorus oxides are solids
Intermolecular forces are weak van der waals and dipole dipole forces
Their melting points are relatively low
Sulfur dioxide and sulfur trioxide are gases at 298K
which oxides are bases?
sodium and magnesium
what does sodium oxide with water to give?
sodium hydroxide solution
strongly alkaline solution
what’s the equation of sodium oxide with water ?
Na2O(s) + H2O(l) ~> 2Na +(aq) + 2OH-
ph of solution 14
what does magnesium oxide react with water to give?
magnesium oxide
sparingly soluble in water and produces a somewhat alkaline solution
what is the equation of the reaction between magnesium oxide and water?
MgO(s) + H2O(l) <~>Mg^2+ (aq) 2OH-(aq)
pH of solution 9
what are the insoluble oxides?
aluminium oxide
silicon oxide
which part of the periodic table oxides form acidic oxides?
non metals on the right of the periodic table
e.g.
phosphorus pentoxide reacts quite violently with water to produce acidic solutions of phosphoric (V) acid
this ionises so the solution is acidic
what do sodium oxide and magnesium oxide react with acids to give?
salt
water
what’s is the equation of the reaction between sodium oxide and sulfuric acid?
Na2O(s) +H2SO4(aq) ~> Na2SO4(aq) + H2O (l)
what is the equation for the reaction between magnesium oxide and hydrochloric acid?
MgO(s) +2HCl (aq) ~> MgCl2(aq) +H2O(l)
does aluminium oxide react with acids or alkalis?
both acids and alkalis
it is called an amphoteric oxide
what is the equation for the reaction between aluminium oxide and hydrochloric acid?
Al2O3(s) +6HCl(aq) ~> 2AlCl3(aq) + 3H2O(l)
what is the equation for the reaction between aluminium oxide and hot sodium hydroxide?
Al2O3(s) +2NaOH (aq) + 3H2O(l) ~> 2NaAl(OH)4 (aq)
how does silicon dioxide react with strong acids?
as a weak acid
e.g. with hot concentrated sodium hydroxide a colourless solution of sodium silicate is formed
what is the equation for the reaction between sodium dioxide and hot concentrated sodium hydroxide?
SiO2(s) + 2NaOH(aq) ~> Na2SiO3 (aq) + H2O(l)
what is the reaction of phosphorus pentoxide with an alkali comparable to?
the reaction of phosphoric(V) acid
H3PO4 because this is formed when phosphorus pentoxide reacts with water
how does phosphoric(V) acid react with sodium hydroxide?
phosphoric(V) acid has three -OH groups
and each of these has an acidic hydrogen atom
so it will react with sodium hydroxide in three stages
as each hydrogen reacts in turn with a hydroxide ion and is replaced by a sodium ion
what are the the three stages of equations involved in the reaction between phosphoric (V) acid and sodium hydroxide?
H3PO4+NaOH(aq) ~> NaH2PO4 (aq) + H2O(l)
NaH2PO4(aq) + NaOH (aq) ~> Na2HPO4(aq) + H2O(l)
Na2HPO4 (aq) +NaOH (aq) ~>Na3PO4 (aq) + H2O(l)
overall equation
3NaOH(aq) +H3PO4 ~> Na3PO4 (aq) + 3H2O(l)
what happens when you add sodium hydroxide to an aqueous solution of sulfur dioxide?
first
sodium hydrogensulfate (IV) is formed
second
sodium sulfate(IV) is formed
what are the equations for when you add sodium hydroxide to an aqueous solution of sulfur dioxide?
SO2(aq) + NaOH (aq) ~> NaHSO3 (aq)
NaHSO3(aq) + NaOH (aq) ~>Na2SO3 (aq) + H2O (l)
what are the trends in melting points
P4O10
SO3
SO2
P4O10>SO3>SO2
this is related to the increase in intermolecular forces between the large molecules
how does sulfur dioxide react with water?
sulfur dioxide is fairly soluble in water and reacts with it to give an acidic solution of sulfuric (IV) acid (sulfurous acid)
this partially dissociates producing H+ ions which cause the acidity of the solution
what is the equation for the reaction between sulfur dioxide and water?
SO2 (g) + H2O(l) ~> H2SO3(aq)
H2SO3(aq) <~> H+ (aq) + HSO3 ^ - (aq)
how does sulfur trioxide react with water?
it reacts violently
produces sulfuric acid
(sulfuric (VI) acid)
what’s the equation for the reaction of sulfur trioxide and water?
SO3 (g) + H2O(l) ~> H2SO4 (aq)~> H+ (aq) + HSO4 ^ - (aq)
what is the equation for the reaction of phosphorus pentoxide and water which then ionises so the solution is acidic?
P4O10 (s) + 6H2O (l) ~> 4H3PO4 (aq)
H3PO4 (aq) ionises in stages
the first being
H3PO4(aq) <~> H+ (aq) + H2PO4^ - (aq)
