All Acronyms. CTA - Control Terminal Agency [Internet]; April 13, 2017 [cited 2017 APR 13]. Available from: https://www.allacronyms.com/CTA/Control_Terminal_Agency.
There are almost 120 known elements. For example, you are made up of billions of billions of atoms but you probably won't find more than 40 elements (types of atoms) in your body. Chemists have learned that over 95% of your body is made up of hydrogen (H), carbon (C), nitrogen, oxygen, phosphorus (P), and calcium (Ca).
Press the 'Check my answer' button after you have entered your answer. If you don't know how to calculate the number of protons, neutrons, electrons or nucleons that are in an atom of an element, reading this page may help you. Would you like to practice only the first 36 elements? Would you like the challenge of having questions with just big atomic numbers?