18858
Structure In common with other Hg ( I ) ( mercurous ) compounds which contain linear X-Hg-Hg-X units , Hg2Br2 contains linear BrHg2Br units with an Hg-Hg bond length of 249 pm ( Hg-Hg in the metal is 300 pm ) and an Hg-Br bond length of 271 pm .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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