What does it mean when work is positive?
a. velocity is greater than kinetic energy.
b. kinetic energy is greater than velocity.
c. the environment did work on an object
d. an object did work on the environment

These models show the electron structures of two different nonmetal elements. which element is likely more reactive, and why? element 1 is more reactive because it has fewer electron shells and is toward the top of its group on the periodic table. element 1 is more reactive because it has more electrons in its valence shell and is farther to the right on the periodic table. element 2 is more reactive because it does not have a valence shell close to the nucleus, so it will attract electrons. element 2 is more reactive because it does not have a full valence shell, so it will attract electrons.

Name three different units of energy used to measure heat and describe what type of situations each is usually used.

Which is not true about oxygen-17 and oxygen-18?