Answer: 12.18 u
Explanation: The average atomic mass of an element is calculated by taking the weighted average of the atomic masses of its stable isotopes.
In other words, each stable isotope will contribute to the average mass of the element proportionally to its abundance.
Answer:
It is heterogeneous as it is made up of visibly different substances or phases.
Because they’re both made up of two substances that are not chemically combined
Explanation:
The generated Na+ and OH-ions are immediately surrounded by molecules of water (typically 6, each). There is the development of the exothermic hydration sphere for each ion. It seems as though there is negative overall energy of dissolving solid NaOH.
Now, since this dissolution is exothermic the temperature of the mixture rises.
Bohr changed the model of the atom by proposing that electrons travelled in circular orbits with specific energy levels.