Group 2 and group 7 elements Flashcards
What happens to the first ionisation energy as you go down group 2 and why?
-decreases down the group
-because each element has an extra electron shell
-more shielding
-less attraction to nucleus, as further away
What happens to reactivity down group 2?
-increases
-electrons further from nucleus are easier to be lost
What is the general trend of melting points down group 2?
-decreases
-the larger the ionic radius, the further away the delocalised electrons are from the positive nuclei
Why does Mg not follow the general trend of melting points?
the arrangement of metallic ions changes
What products are formed when a group 2 element reacts with water?
metal hydroxide and hydrogen
Why do elements react more readily as you go down group 2?
ionisation energies decrease
What happens to the solubility of group 2 hydroxides down the group?
increases
What happens to the solubility of group 2 sulfates down the group?
decreases
How is barium sulfate used in medicine?
-insoluble
-opaque to x-rays
-barium meals –> diagnoses problems in oesophogus, stomach or intestines as it makes tissues look opaque
What is the equation for extracting titanium from its ore?
TiCl4(g)+2Mg(l) –> Ti(s)+2MgCl2(l)
What are the main properties of fluorine at room temperature?
-formula –> F2
-colour –> pale yellow
-physical state –> gas
What are the main properties of chlorine at room temperature?
-formula –> Cl2
-colour –> green
-physical state –> gas
What are the main properties of bromine at room temperature?
-formula –> Br2
-colour –> brown
-physical state –> liquid
What are the main properties of iodine at room temperature?
-formula –> I2
-colour –> grey
-physical state –> solid
Why does the boiling point of halogens increase down the group?
increasing strength of van der waals forces as size and relative mass of molecules increase
Define electronegativity.
the tendency of an atom to attract a bonding pair of electrons
Why do halogens become less oxidising down the group?
-less reactive
-atoms become larger and the outer shell gets further from the nucleus
What are the displacement reactions to identify chlorine?
-add chlorine to bromide ions
-colourless to orange
How do you know bromine is present?
-add bromine to iodide ions
-orange to brown
What is the equation for making bleach?
2NaOH(aq) + Cl2(g) –> NaCl(aq) + NaCl(aq) + H2O(l)
What are the equations for chlorine and water?
Cl2(g) + H2O(l) <–> 2H+(aq) + Cl-(aq) + ClO-(aq)
Cl2(g) + H20(l) <–> 2H+(aq) + 2Cl-(aq) + 1/2O2(g)
(in sunlight)
How do you test for halides?
-silver nitrate test
-add dilute nitric acid
-add silver nitrate solution
-precipitate formed if halide present
Which halides produce white, cream or yellow precipitate?
-white –> chloride ions
-cream –> bromide ions
-yellow –> iodide ions
What colours represent what ions in the flame tests?
-brick red –> calcium
-red –> strontium
-pale green –> barium
With excess OH-, what colour precipitate does magnesium form?
white
How do you test for ammonium ions?
-add sodium hydroxide ions
-damp red litmus paper turns blue if positive
How do you test for sulfate ions?
-add dilute hydrochloric acid
-add barium chloride solution
-white precipitate forms if positive
How do you test for hydroxide ions?
-pH indicator
-red litmus paper
-turns blue if positive
How do you test for carbonate ions?
-add dilute hydrochloric acid
-fizz then positive
-CO2 –> use limewater
-turns cloudy if positive
