inorganic chemistry and the periodic table Flashcards
why does ionisation energy decrease down group 2?
-electron shells of elements increase by 1 down G2
-extra inner shells shield outer electrons from attraction of positive nucleus
-atomic radius increases=outer electrons further away from nucleus=reduction in electrostatic attraction
-these factors make it easier to remove outer electrons∴ionisation energy decreases
does the increase in positive charge of the nucleus (due to extra protons) affect ionisation energy of group 2 elements?
no, effect is overridden by extra shells
what is the trend in reactivity down group 2?
increases down the group
what is the trend in ionisation energy down group 2?
decreases down the group
why does reactivity increase down group 2?
elements of G2 react by losing outer 2 electrons ∴ higher ionisation energies makes it more difficult to lose the outer 2 electrons ∴ will be less reactive
what happens when a group 2 metal reacts with water?
forms a metal hydroxide and hydrogen
Ca + 2H₂O→Ca(OH)₂ + H₂
How does Be react with water?
doesn’t react
How does Mg react with water?
very slowly
How does Ca react with water?
steadily
How does Sr react with water?
fairly quickly
How does Ba react with water?
rapidly- effervescence
what happens when a group 2 metal burns in oxygen?
solid white oxide formed
2Ca + O₂→2CaO
what happens when a group 2 metal reacts with chlorine?
forms solid white chlorides
Ca + Cl₂ → CaCl₂
what are the oxides and hydroxides of group 2?
bases
what happens when oxides and hydroxides of group 2 react with dilute acids?
they neutralise the dilute acids because they are bases,, also form solutions for corresponding salts
what happens when oxides and hydroxides of group 2 react with water?
form alkaline solutions,, more alkaline as you go down the group
why do oxides form more strongly alkaline solutions as you go down the group?
the hydroxides get more soluble
what is the trend in solubility of group 2 hydroxides (and other singly charged ions) down the group?
increased solubility
what is the trend in solubility of group 2 doubly charged negative ions (e.g. SO₄²⁻ sulfates) down the group?
decrease solubility
is barium sulfate completely insoluble?
yes
what substance helps detect carbonate ions and hydrocarbonate ions?
HCl
what happens when HCl and CO₃²⁻/HCO₃⁻ react?
they fizz and give off CO₂
CO₃²(s) + 2H⁺(aq) → CO₂(g) + H₂O(l)
how can you test for CO₂?
lime water goes cloudy
how do you test for sulfates?
HCl and Barium Chloride
how do you identify a sulfate ion?
-add dilute HCl followed by Barium chloride solution
-if white participate of barium sulfate forms it means the original compound contained a sulfate
why is HCl added in the test for sulfate ions?
to get rid of traces of carbonate ions so they don’t affect results
how to test for ammonium compounds?
-damp red litmus paper
-because ammonia gas (NH₃) is alkaline it will turn the red litmus paper blue
how to test for ammonium ions (NH₄⁺)?
-add sodium hydroxide to unknown substance into a test tube and gently heat the mixture
-if ammonia is given off NH₄⁺ ions are present
-this can be tested using damp litmus paper