Group 2 Flashcards
Describe the structure and bonding in any group 2 element
Giant metallic lattice
Strong electrostatic forces of attraction between positive metal ions and delocalised electrons.
Explain why the melting point of magnesium is higher than that of sodium.
The magnesium has a greater ionic charge / more protons/ more delocalised electrons
Magnesium is a smaller atom (has a higher charge density)
So stronger attraction between ions and delocalised electrons.
State and explain which block of the periodic table the group 2 elements belong to.
S block as the highest energy electron is in the s orbital/ sub shell.
What is the definition of an atomic radius?
The distance from the nucleus to the outermost occupied electron energy level.
State Explain the trend in atomic radius down group 2
Atomic radius increases down the group : Down the group electrons are added to new shells which are further from the nucleus and electron shielding increases
Therefore there is less electrostatic forces of attraction between nucleus and outer electron )
What is the definition of first ionisation energy
The energy (enthalpy)needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous positive ions (uni positive)
State and explain the trend in first ionisation energy for group 2 elements.
Ionisation energy decreases going down group 2
This is because atomic radius increases going down the group
This means the outermost electron experiences more shielding meaning weaker electrostatic forces between the nucleus and outer electron
So therefore less energy is required to remove an electron .
Why are group 2 called he alkaline earth metals
Because they form hydroxide compounds.
When they dissolve in water they release OH- ions.(form alkaline solutions)
What is the trend in solubilities of hydroxides in group 2
Solubility increases DOWN the group .
Mg(OH)2 being the LEAST soluble.
Ba(OH)2 being the MOST soluble.
This means that group 2 metals get MORE alkaline down the group.
What is the trend in solubilities of sulfates in group 2.
Solubility decreases DOWN the group
MgSO4 most soluble
BaSO4 least soluble (insoluble)
What happens to stability of the carbonates and nitrates down group 2
Increases down the group
What does thermal stability mean
How Resistant it is to being Broken down by heat
(Thermally unstable a little bit of heat can break the thing down )
How does something become thermally unstable
The electron cloud on the ion becomes distorted
Level of distortion of the electron cloud tells you how unstable that thing is (More distorted less heat required )
Why do we see different colours in flame tests
When we put the G2 in the flame we provide a bit of energy to the electrons
This excites the electron(atomic excitation) and it moves up to a higher electron shell
The electron the comes back down (atomic de-excitation)it emits energy within the visible region (EM spec) so we will physically see the colour
The wavelength is proportional to the energy gap (between energy levels)
This is what gives it a different colour.
How do we conduct a flame test
Clean a platinum or nichrome (a nickel-chromium alloy) wire by dipping it into concentrated hydrochloric acid(removes impurities)
then hold it in a hot (roaring) Bunsen flame. Repeat this until the wire doesn’t produce any colour in the flame.
When the wire is clean, moisten it again with some of the acid and then dip it into a small amount of the solid you are testing so that some sticks to the wire. Place the wire back in the roaring flame again.
