Answer: Helium has the smallest radius.
Explanation: Helium has the smallest atomic radius. Due to nuclear charges and stuff ect-
Answer:
Molar mass = (24.31 + 2 × 35.45) = 95.21 g mol–1 i.e. 95.21 g of MgCl2 is exactly 1 mole.
Explanation:
We know 1 mole of any atom or molecules contains 
atom or molecules.
1 mole of HBr i.e 81 gm/mol contains atom or molecules.
So, mass of 
molecules is :
Therefore, mass of molecules is 1.21 gm .
Hence, this is the required solution.
As you move from left to right across a period,the number of valence electrons<span>-increases. </span>
