<u>Answer:</u> The wavelength of spectral line is 656 nm
<u>Explanation:</u>
To calculate the wavelength of light, we use Rydberg's Equation:

Where,
= Wavelength of radiation
= Rydberg's Constant = 
= Final energy level = 2
= Initial energy level = 3
Putting the values in above equation, we get:

Converting this into nanometers, we use the conversion factor:

So, 
Hence, the wavelength of spectral line is 656 nm
Answer:
the answer to your problem is A.Subscript...BRAINLIEST
Full question options;
(Fe, Pb, Mg, or Ca)
Answer:
Iron - Fe
Explanation:
We understand tht metals pretty much form bonds by losing their valence (outermost electrons). But this question specifically asks for metals that lose beyond their outermost electrons; next to outermost principal energy levels.
Pb, Mg, and Ca only lose their outermost electrons to form the following ions;
Pb2+, Mg2+, and Ca2+.
This is because their ions have achieved a stable octet configuration - the dreamland of atoms where they are satisfied and don't need to go into reactions again.
Iron on the other hand has the following electronic configurations;
Fe: [Ar]4s2 3d6
Fe2+: [Ar]4s0 3d6
Fe3+: [Ar]4s0 3d5
This means ion can lose both the ooutermost electrons (4s) and next to outermost principal energy levels (3d). So correct option is Iron.
Since 1 mole of any element contains 6.0221023 atoms, a mole of carbon and a mole of oxygen will have the same number of atoms.
<h3>Is a mole of oxygen equivalent to a mole of carbon?</h3>
Answer and justification The molar mass of carbon differs from the molar mass of oxygen, hence this assertion is untrue. As a result, one mole of oxygen and one mole of carbon cannot have the same mass.
<h3>What kind of link unites carbon and oxygen?</h3>
A polar covalent link between carbon and oxygen is known as a carbon-oxygen bond. With six valence electrons, oxygen likes to either share two of them in a bond with carbon, leaving the remaining four unoccupied.
To know more about mole of carbon atoms visit:-
brainly.com/question/20484279
#SPJ4