Radon (gas)
The lead of a pencil is made mostly of the nonmetal carbon but the rest of the pencil is neither metal nor nonmetal (except for the bit of metal near the eraser) because it is not an element.
All rare earth elements except promethium have at least one stable isotope.Natural-abundance samples of lanthanum, cerium, neodymium, samarium, europium, gadolinium, erbium, ytterbium, and lutetium are all technically "radioactive" in that they contain measurable amounts of radionuclides, but the half-lives of these nuclides are mostly in the hundreds of millions of years or longer (in some cases much longer).
C, H, Se, Br, I, F, Cl, O, P, S, He, Ne, Ar, Kr, Rn
Curium {Note correct spelling} is only element in the list given that is radioactive and synthetic.^ not correct answer and not even spelled right the correct answer is "lawrencium"The rare earth elements are located at the bottom of the periodic table and are comprised of the lanthanoid series and the actinoid series.The actinoid series is the second row of rare earth elements. All of these elements are radioactive, and all of these elements (except actinium, thorium, protactinium, and uranium) are synthetic.
In drawing a Lewis structure, each nonmetal atom (except hydrogen) should be surrounded by 8 electrons to achieve a full octet and satisfy the octet rule. This can be achieved through the sharing of electrons in covalent bonds or the transfer of electrons in ionic bonds.
Radon (Rn)
Probably you think at radium.
Alkali Metals, except for Hydrogen, which is a Nonmetal.
The lead of a pencil is made mostly of the nonmetal carbon but the rest of the pencil is neither metal nor nonmetal (except for the bit of metal near the eraser) because it is not an element.
The alkali metals are the group 1 elements on the periodic table, except for hydrogen, which is a nonmetal.
All rare earth elements except promethium have at least one stable isotope.Natural-abundance samples of lanthanum, cerium, neodymium, samarium, europium, gadolinium, erbium, ytterbium, and lutetium are all technically "radioactive" in that they contain measurable amounts of radionuclides, but the half-lives of these nuclides are mostly in the hundreds of millions of years or longer (in some cases much longer).
C, H, Se, Br, I, F, Cl, O, P, S, He, Ne, Ar, Kr, Rn
Uranium is not artificial radioactivity so it is not clear what the question is about.
uranium, plutonnium, and not much more except chemicals.
I doubt it, except for normal background radiation for a stone structure.
Curium {Note correct spelling} is only element in the list given that is radioactive and synthetic.^ not correct answer and not even spelled right the correct answer is "lawrencium"The rare earth elements are located at the bottom of the periodic table and are comprised of the lanthanoid series and the actinoid series.The actinoid series is the second row of rare earth elements. All of these elements are radioactive, and all of these elements (except actinium, thorium, protactinium, and uranium) are synthetic.
Plutonium has the same composition as uranium, except for the fact that it contains one more neutron and one more proton. Actually Plutonium-239 has 2 more protons and 2 more neutrons than Uranium-235.