From your knowledge about the distribution of electrons in their shells and from the atomic number (in parentheses), indicate the most likely charge on the ion when this atom forms an ion. (remember the 2-8-18 shell distribution.)

oxygen (8)
a) +1
b) +2
c) -2
d) -1

 -2

Explanation:

Following the shell distribution oxygen has a 2.6. configuration and an electronic configuration of .This means that oxygen has 6 valence electrons that can be used in chemical reactions . In-order to obey the octet rule  it has to gain 2 more electrons to have a  2.8 shell configuration.An electron gain is usually denoted by a negative sign whereas a loss is denoted by a positive sign.Hence the -2   charge on the ion it forms.

explanation:

on disadvantage of hydroelectric power is the cost. another disadvantage of using hydroelectric power is finding a water source powerful enough to harvest hydroelectric power.

ya the other dude is right