OOPS my mistake:
P + Br2 ----> ?
Reaction of phosphorus with the halogens:
White phosphorus, P4, reacts vigorously with all the halogens at room temeperature to form phosphorus trihalides. So, it reacts with fluorine, F2, chlorine, Cl2, bromine, Br2, and iodine, I2, to form respectively phosphorus(III) fluoride, PF3, phosphorus(III) chloride, PCl3, phosphorus(III) bromide, PBr3, and phosphorus(III) iodide, PI3.
P4(s) + 6Br2(g) → 4PBr3(l)
And just afew more:
P4(s) + 6F2(g) → 4PF3(g)
P4(s) + 6Cl2(g) → 4PCl3(l)
P4(s) + 6I2(g) → 4PI3(g)
And for educational purposes:
White phosphorus, P4, reacts with iodine, I2, in carbon disulphide (CS2) to form phosphorus(II) iodide, P2I4. The same compound is formed in the reaction between red phosphorus and iodine, I2, at 180°C.
P4(s) + 4I2(g) → 2P2I4(g)
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Hg + I2 ----> ?
Reaction of mercury with the halogens
Mercury metal reacts with fluorine, F2, chlorine, Cl2, bromine, Br2, or iodine, I2, to form the dihalides mercury(II) fluoride, HgF2, mercury(II) chloride, HgCl2, mercury(II) bromide, HgBr2, or mercury(II) iodide, HgI2, respectively.
Hg(l) + I2(s) → HgI2(s)
And just a few more:
Hg(l) + F2(g) → HgF2(s)
Hg(l) + Cl2(g) → HgCl2(s)
Hg(l) + Br2(l) → HgBr2(s)
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OK this is my I meet you half-way rule...so try the rest and Best of Luck...