When electrons move from the fourth energy level to the second energy level , they emit visible light. why is the light emitted when an electron makes this move in a sodium atom is a different color than the light emitted by an electron moving from the fourth to the second level of a hydrogen atom?

Acurium-245 nucleus is hit with a neutron and changes as shown by the equation. complete the equation by filling in the missing parts. 52

Astudent pours 10.0 g of salt into a container of water and observes the amount of time it takes for the salt to dissolve. she then repeats the process using the same amounts of salt and water but this time she slowly stirs the mixture while it is dissolving. the student performs the experiment one more time but this time she stirs the mixture rapidly. the dependent variable in this experiment is: time for salt to dissolve speed of stirring amount of water mass of salt

Who discovered a pattern to the elements in 1869?