Which of the following groups of elements are in the main group?
O
A. Nonmetals
O
B. Transition elements
O
C. Alkali metals
O D. Halogens

answer: 21

step-by-step explanation:

divide 630 by 30. 30 goes into 630 21 times

ionic bonds are two oppositely charged ions that attract. a sodium ion has a 1 positive charge; a chloride ion has a 1 negative charge. sodium and chloride have oppostive charged ions that attract which forms an ionic bond. a chemical bond formed when two atoms share electrons is called

idk im sorry.

energy per photon is e = h*c / λ  

e = 6.63*10^-34 * 3*10^8 / 6*10^-7 j = 3.315*10^-19 j  

nr. of photons = 10j / 3.315*10 = ^-19 j per photon = 3.02*10^19 photons