Yes, at least 91 elements occur naturally: all of those with atomic numbers of 92 or less except technetium. This still means that the problem "statement" is true, because it does not contain any limiting word such as "only" to modify the number 90. (It is equally true that 2 elements occur naturally.)
Possible... There could be elements in the Earth's crust that have not been discovered yet.
Yes. All elements classified after Element Atomic Number 92 (Uranium) (id est transuranium) are synthesised elements and can not be found naturally. They are also all radioactive, although this is the case for elements from elements 84 onwards.
Most elements are metals.
True
True
true
true
true
It just is not true. Even iron is not naturally magnetic.
earth rotation on its axis causes gravity to occur on earth
False.
false
Yes it is true.
Yes, it is true; chemical elements react to form compounds.
Possible... There could be elements in the Earth's crust that have not been discovered yet.
Yes. All elements classified after Element Atomic Number 92 (Uranium) (id est transuranium) are synthesised elements and can not be found naturally. They are also all radioactive, although this is the case for elements from elements 84 onwards.
that's what ive heard