In a brief paragraph, use your own words to describe the difference in gas composition between Earth's primary atmosphere and its current, secondary atmosphere.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.