Science

1. is a chemical element with symbol He and atomic number 2
6. is a polyatomic ion with the molecular formula NO₃− and a molecular mass of 62.0049 g/mol
7. is a chemical element with symbol N and atomic number 7
9. is a naturally-occurring chemical compound composed of 2 oxygen atoms each covalently double bonded to a single carbon atom
10. in commerce also spelter, is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element of group 12 of the periodic table
11. is a nonmetallic chemical element with symbol P and atomic number 15
12. is a chemical element with symbol Ga and atomic number 31
13. is a chemical element with symbol O and atomic number 8
14. is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system.
17. is a chemical element with the symbol Na and atomic number 11
18. is a chemical element with the symbol S and atomic number 16

1. is a chemical element with chemical symbol H and atomic number 1
2. is a soft and malleable metal, which is regarded as a heavy metal and a post-transition metal
3. is the indigestible portion of food derived from plants
4. is a chemical element with the symbol Ti and atomic number 22
5. is a family of fibrous structural proteins. It is also the key structural component of hair and nails
8. bonding occurs as a result of electromagnetism and describes the electrostatic attractive force that occurs between conduction electrons
9. is a green pigment found in cyanobacteria and the chloroplasts of algae and plants
15. is the chemical element with symbol Ca and atomic number 20
16. is a chemical element with the symbol Mg and atomic number 12