EL8 (Group 2, Periodicity + Ionisation Enthalpies) Flashcards
What is ionisation?
Defined as the removal of one electron from an atom to form an ion.
What is enthalpy?
Energy in kilojoules per mole.
Why does the second and third ionisation enthalpy often require more energy?
The electrons are closer to the nucleus so they feel a greater nuclear attraction.
What are the group 1 metals?
Alkali metals.
Group 2 metals?
Alkaline earth metals.
What ions does G2 form?
2+ as lose 2e- to get full outer shell.
What is the G2 reaction with water?
-Form hydroxides & hydrogen.
-More reactive down group.
What is the reaction of Oxides & Hydroxides?
-Form alkaline solutions.
-More alkaline down group, pH increases.
-Neutralisation reactions.
What is the equation for the thermal decomposition of carbonates?
MCo3(s) = MO(s) + Co2(g)
What does the metal ion do to the carbonate ion?
It distorts the carbonate ion less which means the ionic bond is stronger and needs more energy to break.
Are hydroxides more soluble down the group?
Yes.
What is the pattern of solubility for carbonates?
Less soluble down the group.
what are the general properties of group 2 elements
they are all metallic and shiny, harder than group 1 but softer than transition metals
they have low electro negativity and electron affinity.
explain the pattern of reactivity in group 2
reactivity increases down the group as atom size gets bigger so the distance between the outer shell electrons and the nucleus increases. This decreases the forces of attraction between them so the outer electrons are more easily lost.
what do group 2 react with halogens and hydrogen to form
with halogens to form alkaline earth metal halides and with hydrogen to form alkaline earth metal hydrides.
what is the reaction of group 2 elements with water
to form hydroxides and release hydrogen, the reactions become more vigorous down the group.
why is group 2 less reactive than group 1
because the first and second ionisation enthalpies of group 2 are higher than group 1
describe the uses of 3 group 2 metals
magnesium is used in aircraft construction due to its high strength to weight ratio
calcium is in teeth, bones and shells
barium is used in paints and glass, barium sulphate is used in medical imagine procedures
why does ionisation energy decrease down group 2
the outermost electron shell is further from the nucleus so the distance has increased which causes the electrons to be more easily lost
explain the factor of atomic size in periodicity
atomic radius decreases across a period from left to right and increases down a group.
this is due to a larger nuclear charge pulling electrons in closer and the respective addition of electron shells.
explain the factor of ionisation enthalpy in periodicity
enthalpy increases across a period because there is a higher nuclear charge so the electron is harder to remove.
it decreases down a group due to being further from the nucleus so the attraction is lessened.
explain the factor of electron affinity in periodicity
affinity increases across a period due to the increased nuclear charge.
it decreases down a group due to the increased distance of the valence shell from the nucleus.
explain the factor of electronegativity in periodicity
has the same affect as electron affinity, increases across a period and decreases down a group.
noble gases are not included in this factor as they don’t usually form compounds.
what is electron affinity
the ability of an atom or molecule to attract electrons to itself
what is electronegativity
how strongly atoms attract bonding electrons to themselves
