The principal quantum number (n): specifies the principal shell of the orbital.
The answer is option D.
The important quantum number (n) describes the dimensions of the orbital. Orbitals for which n = 2 are larger than those for which n = 1, as an example. Because they have got opposite electric costs, electrons are interested in the nucleus of the atom.
The numerals, called essential quantum numbers, imply strength degrees as well as the relative distance from the nucleus. A 1s electron occupies the energy stage nearest the nucleus.
A 2s electron, less strongly certain, spends most of its time farther far from the nucleus.
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Answer:
A they share two covalent bonds
Answer: 
Explanation:
For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
Here iron is having an oxidation state of +3 called as
cation and oxide
is an anion with oxidation state of -2. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral
.
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

Answer:
Covalent molecule
Explanation:
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