Answer:
The main difference is their energy level, 2s orbital is higher than 1s orbital.
Answer:
false
Explanation:
because elements never exist in nature as single isotopes they are always combined
The answer is D. element
It's not a mixture, just a pure element. Copper (Cu) is found on the Periodic Table of the Elements, where only ELEMENTS are organized.
Answer:
A hypothesis is something you can test a theory is just a thought that you have.