Hello my friend thank you
Remembering that
d = m ÷ v
d = ?
m = 104 g
v = 21 cm³
Therefore:
d = 104 ÷ 21
<span>d = 4,95 g÷cm³</span>
80 protons,121 Neutrons, and 80 electrons the element is Mercury

☃️ Chemical formulae ➝ 
How to find?
For solving this question, We need to know how to find moles of solution or any substance if a certain weight is given.

Solution:
❍ Molecular weight of 
= 2 × 126.90
= 253.80
= 254 (approx.)
❍ Given weight: 12.7
Then, no. of moles,
⇛ No. of moles = 12.7 / 254
⇛ No. of moles = 0.05 moles
⚘ No. of moles of Iodine molecule in the given weight = <u>0.05</u><u> </u><u>moles </u>
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