EL 8 Flashcards
what is ionisation enthalpy
the amount of energy needed to remove electrons attracted to the nucleus
(energy needed to form a positive ion)
what is the general formula for the first 2 ionisation enthalpies
X (g) —- X+(g) + e-
X+ (g) —- X2+(g) + e-
X = element in gaseous form
what happens to the ionisation enthalpy as you increase the groups
ionisation enthalpy increases in a period as there are more electrons in the outer shell
more energy needed to remove outer electron since force of attraction between electrons and nucleus is stronger (more protons than electrons)
trends in the s block of the periodic table
elements become more metallic as you go down a group
most reactive elements found at the bottom of the group (increased shielding since electrons are further away from nucleus, weaker force of attraction)
elements become less metallic across a period
what are the similarities and difference of elements reactivity in a group
similarity in reactivity-
elements have a similar arrangement of electrons in the atoms
differences in reactivity-
size of atom increases down a group
how does atomic radius of an atom effect the ionisation enthalpy
atomic radius -
the greater the atomic radius the smaller the force of attraction between the nucleus and the outer electrons
what happens to the atomic radius across a period
atomic radius gets smaller as there is one more proton so the force of attraction between the nucleus and outer electrons is stronger
shielding stays the same
how does nuclear charge of an atom effect ionisation enthalpy
the greater the nuclear charge the stronger the force of attraction between the outer electrons and the nucleus
how does electron shielding of an atom effect the ionisation enthalpy
the greater shielding (more electron shells) the less energy it takes to remove the outer electrons since the nuclear attraction is weaker
what happens to the atom during successive ionisation enthalpy
as each electron is removed there is less repulsion between the electrons and each shell is drawn closer to the nucleus
nuclear attraction between the outer electrons and nucleus increases since there is one less electron
ionisation enthalpy increases since more energy will be needed to remove the outer electron
what is formed when group 2 elements react with water
metal hydroxides
e.g. Sr(s) + 2H20(l) —- Sr(OH)2(aq) + H2(g)
metal hydroxide
what is formed when group 2 elements react with oxygen
metal oxides
2Mg(s) + O2(g) —- 2MgO (s)
metal oxide
(group 2 oxides are white solids)
what is formed when group 2 elements reacts with water
alkaline solution
SrO(s) + H2O(l) —- Sr(OH)2(aq)
SrO(s) + H2O(l) —- Sr2+(aq) + 2OH-(aq) written in ion form
group 2 elements become more strongly alkaline down the group since hydroxides become more soluble
can neutralise acids
group 2 solubility rules with charges
if anion has a double charge like carbonates (CO32-) then it becomes less soluble down group 2
if anion has a single charge like hydroxides (OH-) then it becomes more soluble down group 2
what do carbonates break down into in group 2
metal oxides + carbon dioxide
occurs via thermal decomposition
e.g. CaCO3 —- CaO + CO2
what happens to the production of carbon dioxide as you go down group 2
less CO2 is produced
e.g.
100g of MgCO3 will make 52.2g of CO2
100g of BaCO3 will make 22.3g of CO2
what happens to the thermal stability of carbonates down group 2
carbonates become more thermally stable down group 2
how do group 2 carbonates become more thermally stable down the group
carbonate ion has large electron cloud that can be distorted by nearby positive group 2 ions
group 2 metal ion 2+ charge becomes larger down the group meaning charge is spread out over a larger area
this means that charge density decreases down group 2
the higher the charge density of the metal ion the more it distorts the electron cloud making the carbonate less stable
