Are zeros considered significant figures in scientific notation?

[gunblaze]

ok...

So We got 2 number (i) 34500000000 & (ii) 30.4 <both to 3 sig fig>

is zero considered a significant figure in this case...? If it is, then why do we include the zeros in 34500000000, if it is not, why, 30.4 and not 30.44?

 

[tigger]

zero in the middle of non-zero numbers is always counted as a sigfig
but if it's the last number.. then it may or may not be counted as sigfig
if it's the first one, it is not a sigfig (e.g 0.0002 --> 1 sigfig)

 

[honestrosewater]

The basic idea behind the rules is that if zero is merely acting as a place-holder, it isn't counted as significant. The rules rely partially on convention to remove ambiguity, so there really is no substitute for just learning the http://www.swt.edu/slac/math/SigFigur.html .
As tigger said, (i) is ambiguous as written. See Rule 5 in the link.