I believe the answer you are looking for is the 4th one.
The best answer is the isotope of strontium which is strontium-85. It has a half-life of about 64 days. The metal strontioum has four stable, naturally occurring isotopes which includes 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%).
Answer:
The atomic mass on the periodic table is a decimal number because it is an average of the different isotopes of an element.
P.S.
An isotope is each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.
Answer:
true
Explanation
Unbalanced forces can cause an object to change its motion.If an object is at rest and an unbalanced force pushes or pulls the object it will move. Unbalanced forces can also change the speed or direction of an object that is already in motion.
