Period 3 Flashcards
Across period 3, shielding…
stays the same
across period 3 the nuclear charge
increases as we go across
therefore across period 3 the nuclear attracts the electrons
more
across period 3 the atomic radius
decreases
the first ionisation energy across period 3 generally
increases
moving across a period number of electron shields remain the same so shielding remains the same
however nuclear charge increases therefore attraction between nucleus and outermost electron increases
Explain why the first ionisation energy of aluminium is less than magnesium
The outermost electron of aluminium is in a P orbital whilst magnesium is in an S orbital
electrons in the S orbital repel and shield the electrons in the P orbital to some extent
this means less energy is required to remove the first electron in the P orbital of aluminium
therefore aluminium has a lower first ionisation energy
explain why the first ionisation energy of sulphur is less than phosphorus
phosphorus has only 1 electron of its p orbital
sulphur has 2 electron in one of its p orbitals causing increases electron repulsion
meaning less energy is required to remove an electron from sulphur
therefore sulphur has lower first ionisation energy than phosphorus
Which of these form metallic bonding
Sodium Magnesium Aluminium Silicon Phosphorus Sulphur Chlorine Argon
Sodium , Magnesium and aluminium are all metals
therefore are held together by metallic bonding
In period 3, the elements from phosphorus to chlorine all form…
What is argon?
What is silicon
covalent bonds.
Argon is inert and doesn’t really form bonds
Silicon is neither a metal or non metal so it’s a metalloïd and forms many strong covalent bond the result is a giant covalent lattice
What is the trend between the first period 3 elements of Na, Mg and Al
explain the reason why?
Na < Mg < Al
Na is lower melting point than magnesium
Magnesium has a lower melting point than aluminium
moving from sodium to aluminium the charge on the metal cation increases an snubber of delocalised electrons per cation increases
therefore attraction between the metal cation and delocalised electrons increased and strength of metallic bonding increases
Between Silicicon, Phosphorus, Sulphur, Chlorine and argon rank the melting points from 1(highest) to 5 (lowest
Silicon 1 phosphorus 3 sulphur 2 chlorine 4 argon 5
How many atoms are in a molecule of
Phosphorus Sulphur Chlorine Argon l
Phosphorus = 4 Sulphur = 8 Chlorine = 2 Argos = 1
Explain why phosphorus has a lower melting point than sulphur
Phosphorus exists as P4 molecules whilst Sulphur exists as S8
therefore sulphur is bigger than phosphorus and sulfur has more electron than phosphorous
meaning van der waals forces are stronger so more energy is required to break the intermolecular force of sulphur compared to phosphorus
Predict the general trend in atomic radius across period 5 and why
atomic radius decreases
because nuclear charge increases and there is more attraction between the outermost electrons and the nucleus
predict the general trend in the first ionisation energy across period 5 and why
first ionisation energy increases because nuclear charge increases an ethereal is more attraction between the outermost electrons and the nucleus
Between which period 2 element does the first ionisation energy decrease?
beryllium and boron decrease between group 2 and 3
and nitrogen and oxygen decrease between group 5 and 6
period 2 has the same trend in the first ionisation energy as period 3
Complete the balanced equation
2Na (s) + 2H2O —>
2Na (s) + 2H2O —> 2NaOH (aq) + H2 (g)
State the full balanced equation for the reaction between magnesium and steam
Mg (s) + H2O (g) —> MgO (s) + H2 (g)
the reaction of cold water with sodium is
faster than the reaction of cold water with magnesium
Magnesium hydroxide forms a much less alkaline solution because it has a much lower
solubility than sodium hydroxide
Give the formula of the highest oxide of Sodium magnesium aluminium silicon phosphorus sulphur
sodium = Na2O magnesium= MgO Aluminium = Al2O3 Silicon = SiO2 Phosphorus = P2O5 sulphur = SO3
What is observed when the sodium magnesium red phosphorus white phosphorus sulphur are heated with oxygen?
Sodium = white powder and yellow flame flame forms
magnesium = white powder and white flame forms
red phosphorus= white powder and white smoke forms
White phosphorus = white powder and white smoke forms
sulphur = blue flame forms
What are the oxidation states of sulphur in the following molecules
H2S
SO2
H2S = -2 SO2 = +4
Give the chemical formula for sulfur (IV) oxide
SO2
Which of the following oxides form ionic lattices? Na2O MgO NO K2O SiO2
Na2O, MgO and K2O
What holds a SO2 molecule together ?
covalent bonds because sulphur and oxygen are both non metals
non metals are held together in molecules by covalent bonds
What force exists between molecules of SO2
van der waals and dipole dipole forces
all covalent molecules experience intermolecular forces
all covalent molecules experience van der waals forces
SO2 has a dipole n will experience dipole dipole forces
How many oxygen atoms are there in the highest oxide of Phosphorus and sulfur?
phosphorus = 5, 10 sulfur = 3
Giant lattices can be macromolecules or ionic lattices
what do we know
ionic lattices consist of oppositely charged ions
and both types of structures have very high melting points relative to molecular lattice
Explain the following melting point trend
P4O10 > SO3 > SO2
all 3 form molecular lattices & held together by intermolecular forces meaning we must consider van der waals which depend on size of molecule
the size of molecules follow the trend P4O10 > SO3 > SO2
therefore melting point also follows the same trend as the arrow
explain how covalent cb drafter of aluminium oxide arises
aluminium cation is very small
meaning aluminium cation is closer to the oxide ion
the cation is also very highly charged enough to distort the electron cloud
therefore electron cloud appears more covalent
What oxide reacts with water to form an acidic solution?
P4O10 , SO2 and SO3
Predict the pH of 1 mol dm -3 of the final something when the following reacts with water MgO SO3 P4O10 Na2O
MgO = 9/10
SO3= 0/1
P4O10= 1/2
Na2O =13/14
Why doesn’t SiO2 react with water?
water can’t break apart the giant covalent lattice of SiO2
State the equation for the reaction. between sulfuric trioxide and water
and sulfur dioxide and water
SO3 (l) + H2O (l) —> H2SO4 (aq)
SO2 (g) + H2O (l) —> H2SO3 (aq)
moving across period 3 the ph in aqueous solution if the highest oxides …
decreases
silicicon dioxide reacts with
strong bases
write the balanced equation for the reaction between silicon dioxide and hot concentrated sodium hydroxide
SiO2 (s) + 2NaOH (aq) —> Na2SiO3 (aq) + H2O (l)
Phosphorus (V) oxide reacts with
water and bases
write the balanced equation reaction for the over reaction between phosphorus oxide and potassium hydroxide
P4O10 (s) + 12KOH —> 4K3PO4 (aq) + 6H2O (l)
what oxide forms a base without forming an acid when added to aqueous alkaline solution ?
SiO2 and SO2
as P4O10 and SO3 react vigorously with water so that effectively tbh eur reaction with an alkaline aqueous solution happens in 2 stages
first they react with water to form an acid
then secondly the acid reacts with the base
reaction of these 2 stages is the same as the direct reaction which would occur in absence of water
SO2 (aq) + 2NaOH (aq) -> .. (aq) + H2O (l)
SO3 (l) + 2NaOH (s) —> … (aq) + H2O (l)
state the missing product in these equations
1) Na2SO3
2) Na2SO4
