which 2 element do not exist by themselves in nature?
2006-09-20 14:07:58 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Biology
43- Technetium
61- Promethium
85- Astatine
87- Francium
only technetium and promethium doesnt have any isotopes
All of the other synthetic elements are transuranium. It is quite simple to explain why they don't exist naturally. Tc however has a low atomic number/mass and is flanked by stable elements.
Francium is found in uranium minerals, and can be made artificially by bombarding thorium with protons. It is the most unstable of the first 101 elements. The longest lived isotope has a half-life of 22 minutes. This is the only isotope of francium occurring in nature, but at most there is only 20-30 g of the element present in the earth's crust at any one time. No weighable quantity of the element has been prepared or isolated.
Astatine is radioactive and essentially unavailable in nature. It is
not possible to make other than in a nuclear reactor.
2006-09-20 17:30:53 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Technetium and Promethium. They are not found on Earth in nature, but they have been found in certain stars by spectroscopy, so they do occur "in nature".
2006-09-20 14:14:25 · answer #2 · answered by Sciencenut 7 · 0⤊ 0⤋
How about oxygen and nitrogen. They don't exist as O or N...but rather as O2 and N2.
2006-09-20 14:15:21 · answer #3 · answered by The Terminator 2 · 0⤊ 0⤋
The diatomics. Oxygen, being one. You have to think of the other.
2006-09-20 14:15:35 · answer #4 · answered by Anonymous · 0⤊ 0⤋
what kind of homework is this?!
2006-09-20 14:11:09 · answer #5 · answered by :: [ DARK GHOST ] :: 2 · 0⤊ 0⤋
You tell us
2006-09-20 14:09:12 · answer #6 · answered by Anonymous · 0⤊ 0⤋
you and me
2006-09-20 14:09:17 · answer #7 · answered by Rammohan 4 · 0⤊ 0⤋