Answer:
Physical boundaries
Explanation:
Physical boundaries are a type of boundary that separates territories or countries according to natural features in the landscape, such as mountains, rivers or deserts. The Mekong border between Myanmar and Laos is an example of physical boundaries.
Answer:
Wilhelm Wendt was the first I think
Answer:
The elements with the same atomic number but different mass are called isotopes.
Explanation:
Isotopes are atoms of the same element that differ in the number of neutrons in their nuclei. That is, isotopes are atoms that have the same atomic number - equal numbers of protons - but different atomic mass - different number of neutrons. Their chemical properties, however, do not differ.