Final answer:
In RNA, a triplet of nucleotides, known as a codon, codes for a single amino acid. Nitrogen, with an atomic number of seven, has two electron shells with its electron configuration.
Step-by-step explanation:
The number of 'letters' in an RNA molecule, in sequence, that provides the code for a single amino acid is three. These 'letters' are nucleotides, and a group of three nucleotides is called a codon. Each codon corresponds to a specific amino acid or a stop signal during protein synthesis through the process of translation.
In the case of Nitrogen, which has an atomic number of seven, it is likely to have two electron shells. The atomic number tells us the number of protons and electrons in a neutral atom, and electron distribution follows a specific order: the first shell can hold up to two electrons, while the second can hold up to eight. Nitrogen, with seven electrons, fills the first shell and has five electrons in its second shell.