How have safety concerns about chemicals changed over time? A.
Government officials rather than scientists decide what chemicals are dangerous.
B.
As scientists have learned more about chemicals, they have become more aware of their dangers.
C.
All nations have agreed to a set of safety standards, so testing chemicals is no longer necessary.
D.
Scientists are no longer as concerned about chemicals because they are much safer today.

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8