Answer:
Explanation:
19) it is 3d10 instead of 4d10
20) it is missing 3p6, and 4s2 before 3d5
21) Ra is not a noble gas
22) Cs is not a noble gas
About 1 gram. 1 part of 50 is 2%
Atomic mass is the quantity of protons that have in a atom. Which atom have different numbers of protons, being able to be identified by them.
hydrogen and helium and the most abundant elements in a nebula.