Naturally occurring antimony consists of 57.25
%

121
Sb
57.25
%

121
Sb
, which has a mass of
120.9

u
120.9

u
and
42.75
%

123
Sb
42.75
%

123
Sb
, which has a mass of
122.9

u
122.9

u
. Calculate the average atomic mass of antimony with the correct number of significant figures.

its first and third is your answer i did the qustion the fourth isnt right

the transfer of heat by electromagnetic radiation is called thermal radiation . it is usually carried out by electromagnetic waves in an energy range just below the visible spectrum, which is the infrared range.

so the answer would be radiation.

: )