Ms. Smith told her students to do 30 jumping jacks without stopping. When everyone had completed the jumping jacks, she asked the students to look around and observe each other. She said, "What do you notice about each other that is different from before you did the jumping jacks?" The changes that the students observed, rapid breathing and sweating, would be classified as a to a change in a system.
A)limit
B)response
C)stimulus
D)feedback mechanism

increased stability in the completion of fluorine's outer shell.

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.