Using the periodic table, which of the following is an isotope? zn – 68 tb – 159 cs - 133 c – 12

An isotope occurs when the number of neutrons in an atom doesn't equal to amount of protons. A neutral atom has same number of protons as neutrons. So, if the number next to it isn't 2 times the atomic number, then that choice is an isotope. For example: If I had a Carbon atom, I know it has 6 protons, b/c its atomic number is 6. But, my atom only has 5 neutrons, not 6 neutrons. So it's an isotope. It will be labeled Carbon-11. The '11' comes from the sum of protons and neutrons.

Ithink this is what you meant. the temperature at which a liquid begins to boil is called the boiling point. the boiling point of water is 212°f or 100°c.  and at that point will start to turn into steam (gas)

You can still be friends with each other. you don't have to date since he likes someone else. just stick to being friends for now