Element x reacts to form xo. it has the second smallest radius of its group. what is element x?
li
ba
mg
be

Li

Explanation:

Is the element of the first group and is the second smallest of its group. Even Magnesium is in the same situation, but if you compare the atomic radius of lithium and magnesium, the first one is smaller.

Barium definitely is incorrect because is the one that has the biggest radius of its group.

Beryllium is the first of its group so it can not fit the description.

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.