What is released when an excited electron returns to a lower energy state? an isotope
a proton
electricity
electromagnetic radiation

Molten iron fills a mould, which has a volume of 200 cm cubed. calculate the volume when the iron cools and solidifies.

Waves that cause the most damage during an earthquake are a. surface waves c. s waves b. p waves d. ocean waves

Examine the equation. 23490th→23088ra+42he what kind of barrier would you need to block the radioactive particles from this reaction? a.a piece of paper b.a sheet of aluminum foil c. a two-inch block of lead d. a solid concrete block