Which of the following are always the same for atoms of the same element?

What happens to the composition of an atom to cause it to become positively or negatively charged?

When your working with the passage-based reading questions on the psat do all of the following except. a)make sure you read each question throughly. b) try to answer each question before you look at the answers. c) plan to spend most of your time reading the passage. d) make sure your answer choice is the most correct number me

What did pavlov initially notice about the animals in his original research after conditioning took place?