Place the following elements in order of decreasing atomic size: antimony, selenium, fluorine, rubidium, strontium, and arsenic.

ANTIMONY

STRONTIUM

RUBIDIUM

ARSENIC

SELENIUM

FLOURINE

Explanation:

ATOMIC SIZE INCREASES FROM TOP TO BOTTOM and DECREASES FROM LEFT TO RIGHT.

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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.