Shameeka is studying for an exam. She took the notes below about calcium and chlorine, which are known to form ionic bonds. Calcium, which is a metal, donates 2 electrons to chlorine.
The individual calcium atoms become ions with a negative 2 charge.
The bond between calcium and chlorine makes the atoms stable.
Calcium and chlorine attract each other.

In an experiment examining the effects tai chi on arthritis pain, callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. half of the participants immediately began a tai chi course and the other half (the control group) waited 8 weeks before beginning. at the end of 8 weeks, the individuals who had experienced tai chi had less arthritis pain that those who had not participated in the course.