Answer:
A. there is an isotope of lanthanum with an atomic mass of 138.9
Explanation:
By knowing the different atomic masses of both Lanthanum atoms, we can not tell anything about their occurence in nature. Therefore, all the last three options are incorrect. Because, the atomic mass does not tell anything about the availability or natural abundance of an element.
Now, the isotopes of an element are those elements, which have same number of electrons and protons as the original element, but different number of neutrons. Therefore, they have same atomic number but, different atomic weight or atomic masses.
Hence, by looking at an elements having same atomic number, but different atomic masses, we can identify them as isotopes.
Thus, the correct option is:
<u>A. there is an isotope of lanthanum with an atomic mass of 138.9.</u>
Answer:
yes
Explanation:
because they are all the same revolving round the sun the colors only differ
Answer:
Particles of matter possess energy called kinetic energy.
Solid cannot be compressed, but gases are highly compressible.
The Kinetic energy of molecules of gases is very large & solids the least.
On heating a sublimable liquid, the molecules break free & escape from the surface of the solid directly into vapour.
Particles of matter move more rapidly on the application of heat
However, as a result of the Sun's large angular size, solar<span> illumination is only partially blocked in the outer portion of the Earth's </span>shadow<span>, which is given the name penumbra. A penumbral </span>eclipse<span> occurs when the Moon passes through the Earth's penumbra. The penumbra causes a subtle darkening of the Moon's surface.</span>
Rust does not have the properties to catch onto flames. However, if you light it on fire, then it would probably catch in flames but not instantly and will not continue to burn unless you have soaked it in oil or flammable object or substance. :) Hope this helps!
