Periodicity, Group 2 and Group 7 Flashcards
horizontal rows of elements are called ….
periods
vertical columns of elements are called…
groups
elements in a group have the same number of …
outer shell electrons
metals are ____ conductors of electricity
good
non-metals are _______ conductors of electricity
non
metalloids are ________ conductors of electricity
poor
s-block elements have their highest energy outer-shell electron in the _ orbital
S
Describe the trend in atomic radii across a period (5 marks)
Protons are added to the nucleus so nuclear charge increases.
Electrons are added to the same shell.
The nuclear attraction on the outer shell electrons increases across a period.
The electron shells are drawn inwards by the nucleus, making the atoms smaller.
so atomic radii decreases across a period.
Describe the trend in atomic radii down a group (5 marks)
The number of shells increases
The outer electron is added to a new shell which is further away from the nucleus.
The shielding effect by the inner shell electrons increases down a group.
The nuclear attraction decreases down a group
So the atomic radii increases down a group.
A substance has a high melting or boiling point if the bonds broken are (1). The structure of the substance is (2).
- Strong
- Giant
A substance has a low melting or boiling point if the bonds broken are (1). The structure of the substance is (2).
1.Weak
2. Simple
Across each period there is a sharp decrease in melting and boiling points between Group 4 and 5. Explain why.
Structures change from giant to simple.
Why is the boiling point of aluminium much higher than that of sulfur
Aluminium is a giant metallic structure whereas Sulfur is simple covalent.
Aluminium has stronger bonds, takes more energy to overcome and break the bond.
explain why Phosphorus (P4) has a higher boiling point than Chlorine (Cl2).
P4 has more intermolecular forces to break so more
energy is needed than Cl2 molecules. Whereas Cl2 is a smaller molecules so can break bonds quicker.
P4 has more electrons than Cl2.
Define first ionisation energy
First ionisation energy is the energy required to remove one electron from each atom in one mole of gaseous atoms, to form one mole of gaseous 1+ ions.
the more (1) in the nucleus, the greater the nuclear charge. The greater the nuclear charge, the stronger the nuclear (2) on the outer electrons. Therefore a higher nuclear charge means (3) energy would be needed to overcome the attraction between the nucleus and the outermost electron.
- proton
- attraction
- more
As the distance between the outmost electron and the nucleus increases, the attraction between them (1). The weaker the nuclear attraction, the (2) energy is needed to remove the outer electron
- decreases
- less
Electron shielding is the shielding between electrons in different (1) shells. This shielding effect reduces nuclear attraction. The more inner shells there are, the (2) the shielding effect and the (3) nuclear attraction.
- inner
- more
- less
First ionisation energy (1) down a group
there are (2) shells
more (3) effect ( from inner shell electrons)
the atomic radius (4).
the (5) on the outer shell electrons decrease
(6) energy is needed to remove the outer electron
- decreases
- more
- shielding
- increases
- nuclear attraction
- less
First ionisation energy (1) across a period
the outer electron fills the (2) shell so (3) stays the same.
the atomic radius (4)
therefore there is a greater (5) on outer electrons
(6) energy is needed to remove the outer electron.
- increase
2.same - shielding
- decreases
- nuclear attraction
- more
state and explain which element has the highest first ionization energy:
Carbon and Nitrogen
Nitrogen.
Nitrogen has a smaller atomic radius
But similar shielding
More attraction to the outer shell electron as it has more protons. More energy needed to break the nuclear attraction.
state and explain which element has the highest first ionization energy:
Potassium and Lithium
Lithium.
less electron shells, smaller atomic radius.
less shielding.
Nuclear attraction increases, more energy required to loose outer electron
State and explain which element has the highest first ionization energy:
Magnesium and Aluminium
Magnesium.
Aluminium outer electron lies in p-orbital, further from the nucleus.
less nuclear attraction
same shielding
aluminium looses outer electron easier.
State and explain which element has the highest first ionization energy:
Phosphorus and Sulfur
Phosphorus:
Sulfur has a pair of electrons in it’s orbital.
electron pair repels
easier to loose its outer electron
same shielding
Define successive ionization energies.
Successive ionization energies are a measure of the energy required to remove each electron in turn.
write an equation for the second ionization of sodium.
Na+(g) ——–> Na2+ (g) + e-
write an equation for the seventh ionization of bromine
Br6+(g) ———> Br7+ (g) + e-
explain why successive ionisation energies increase with ionization number. (4)
once an electron has been removed, there are the same number of protons but fewer electrons
proton : electron ratio increases
remaining electrons are more strongly attracted to the nucleus
more energy is needed to remove each electron in turn.
what does the largest jump in ionization energy show about an element
its group number -
the largest energy jump shows a removal of an electron from a new inner shell.
what structure do all group 2 elements have?
giant, metallic
why are the group 2 metals good conductors
contain mobile, delocalised electrons which can move to carry a charge.
does a group 2 metal have a high or low melting/boiling point. Give a reason for your answer.
High melting and boiling point.
A lot of energy is required to break the strong metallic bonds.
do group 2 metals undergo oxidation or reduction
oxidation.
forms 2+ ions which is a loss of electrons
does atomic radii decrease or increase down group 2
increases
why does atomic radii increase down group 2
more shells, increase shielding effect.
increase distance of outer electron to the nucleus
nuclear attraction decreases down the group
therefore atomic radius increases.
first ionization energy will decrease down the group.
does first ionization energy increase or decrease down group 2
Decrease
metal + oxide ———>
metal oxide
metal +water ———–>
metal hydroxide + hydrogen
magnesium + steam ——->
magnesium oxide + hydrogen
metal oxide + water ——–>
metal hydroxide
describe the solubility of the group 2 metal hydroxides in water
Increases down the group.
Results in solutions more alkaline down the group
does the solubility of group 2 metal sulfates in water increase or decrease down the group.
Decreases
Explain why Ba(OH)2 (aq) has a greater pH than Ca(OH)2 (aq)
solubility increases down group 2
alkalinity increases as hydroxide ions can be separated easier.
Use of Mg(OH)2 and why?
used in indigestion tablets as an antacid
Neutralises excess stomach acid safely because it is a mild alkali
Use of Ca(OH)2 (s)
used in agriculture to neutralise acidic soil
Use of BaSO4 (s) and why ?
used for visualising X-rays
It is insoluble so does not release toxic barium ions into patients bloodstream.
What does a group 2 metal carbonate form when undergoing thermal decomposition?
Metal Oxide + Carbon Dioxide
Thermal decomposition of group 2 metal carbonates gets harder going down the group. This means thermal stability (1) down the group.
increases
true or false
elements in group 7 exist as diatomic molecules with covalent bonds
true
do the halogens have high or low boiling points, why is this?
low
little energy is needed to overcome the weak london forces between molecules
true or false
melting/boiling points decrease down group 7
false.
melting points increase down group seven as there are more shells so more london forces to break.
the halogens are ______ oxidising agents
strong
(oxidising power decreases down the group)
reactivity decreases down group 7
what does this tell you about fluorines oxidising power
fluorine is the strongest oxidising agent out of the halogens. This means it is also the most reactive.
why does reactivity decrease down group 7
There are more shells , atomic radius increases
Greater shielding effect by inner shell electrons
There is weaker nuclear attraction
The nucleus is less able to attract and capture another electron into its outer shell.
what is the colour of Cl2 when dissolved in water
pale-green
what is the colour of Br2 when dissolved in water
orange
what is the colour of I2 when dissolved in water
brown
what is the colour of Cl2 when dissolved in organic solvent
pale-green
what is the colour of Br2 when dissolved in organic solvent
orange
what is the colour of I2 when dissolved in organic solvent
purple
define disproportionation
A reaction in which the same element is both oxidised and reduced
write the reaction for disproportionation of chlorine in water. what is this reaction most commonly used for?
Cl2(aq) +H2O(l) ——> HClO(aq) + HCl(aq)
used to kill bacteria in the treatment of water
what is the disadvantage of using chlorine to treat water
chlorine is toxic
write the reaction for the disproportionation of chlorine in aqueous sodium hydroxide. what is this reaction most commonly used for?
Cl2(aq) + 2NaOH(aq) ⇌ NaCl(aq) + NaClO(aq) + H2O (aq)
used to make household bleach
what are the condtions needed for NaOH to react with Cl2 to form household bleach
NaOH must be cold, dilute and aqueous
what is the colour of AgCl (s)
white
what is the colour of AgBr (s)
cream
what is the colour of AgI (s)
yellow
True or False
AgCl (s) is soluble in dilute ammonia
true
True or false
AgBr (s) is soluble in dilute ammonia
false
only soluble in concentrated ammonia
True or False:
AgI (s) is insoluble in ammonia
True , precipitate will not dissolve.
