The correct answer would be the fourth option. A nucleotide consists of a phosphate group, a pentose sugar, and a nitrogen containing base that are all linked together by covalent bonds. Nucleotides are the monomer units of nucleic acids and is the basic unit of the DNA.
Protons: charge +1, have a mass of 1 and are found in the nucleus
Neutrons: charge 0, have a mass of 1 and are found in the nucleus
Electrons: charge -1, have a mass of 1/840 and are found on the outside of the nucleus
hope that helps
Nitrogen is 5 valence electrons
oxygen is 6 valence electrons
fluorine is 7 electrons
