inorganic: properties of G7 Flashcards
explain the reactivity, atomic radius and ionisation energy of group 3
radius increases down the group due to increases shells, reactivity decreases due to this as the shielding reduces the attraction to a new e- as it needs to gain one for full outer shell, ionisation energy also decreases due to this as more shielding lowers attractions so less energy required to remove outer e-
explain the m/bp of elements in g7 in terms of bonding and structure
simple covalent molecules so Vdws hold together, the bp increases down group due to the atom becoming larger/ Ar larger so more e- so more stronger Vdw forces so more energy required to overcome them
explain the volatility of group 7
Volatility refers to how easily a substance can evaporate
the higher the boiling point the less volatile, I has higher bp so solid at room temp so less volatile, and Cl is gas at room temp with low bp so very volatile
Explain the oxidising power of group 7 elements
they are good oxidising agents as they accept e-, however down the group the oxidising power decreases due ( decrease in electronegativity linked to size of atom) to less nuclear attraction over the shielding to accept more e-
due to this a halogen will displace the halide ion beneath it, flourine is
cl2 will displace br- I-
br2 will displace I-
i2 wont displace anything
define electronegativity
ability for an atom to attract a pair of e- to its nucleus in a covalent bond
what is the trend in electronegativity in group 7
decreases down group due to less attraction from nucleus as bigger atom has more shielding so less ability to attract pari of e-
explain how displacement reactions occur with group 7 elements
A more reactive halogen can displace a less reactive halogen from a halide solution of the less reactive halogen
Explain the reducing power of halide ions
the reducing power increases going down the group as they donate e- and themselves are oxidised
going down the group the ion becomes larger so outermost e- further due to more shielding so more easily lost
testing for halide ions
1) dilute solution and dissolve in nitric acid and add silver nitrate
agcl-white agbr-cream. agi-yellow
Add dilute NH4 to distinguish
agcl will dissolve agbr wont
Add conc ammonia
agbr will redissolve agi wont
2) in fume cupbourd since toxic gases add conc H2SO4(l) + X-(aq) → HX(g) + HSO4-(aq)
results
cl- steamy fumes
br- fumes, brown fumes, s02
i- fumes, purple gas, h2s bad smell, s yello, so2 colourless gas
explain reactions of halide ions with concentrated sulfuric acid
H2SO4 + NaCl—- HCl ( steamy white fumes) + NaHSO4
H2SO4 + NaBr —- HBr + NaHSO4
H2SO4 + 2NaBr— Br g (brown fumes) + So2 g + 2H2O
H2SO4 + NaI — HI + NaH2SO4
2HI +H2SO4 — I2 (purple fumes) + SO2 + 2H20
6HI +H2SO4— 3I2 + S (Yellow solid) + 4H20
8HI + H2SO4 — 4I2 + H2S (bad smell)+ 4H20
state Cl2 reaction with water
cl2 +H2O — HCL + HCLO in cold water this is a disproportionation reaction as cl oxidation number us +1 and 1- and used to purify water for drinking and also a bleach
2Cl2 + 2H2o — 4HCL + O2 due to uv light
state reaction with sodium/calcium chlorate
H2O+ NaClO — Na+ + OH- + HCLO
this is a reversible reaction m(equilibrium)
state reaction of Cl2 with NaOH (alkali)
Cl2 +NaOH — NAClO + NACl + H2O
