The number of electrons that fills a certain principle energy level equals
a-n
d-n²
b- 2n
c- 2n²

option c = 2n²

Explanation:

Principle energy levels are represented by n. The number of orbital per energy level are determine through n². While the number of electrons in per energy level are determine through 2n².

For example:

Principle energy level n    number of orbitals n²       number of electrons 2n².

            1                                            1² = 1                         2(1)²  =2  

           2                                           2² = 4                        2(2)² = 8

           3                                           3² = 9                        2(3)² = 18

while the number of electrons in subshell can be determine through Aufbau principal.We know that there four subshells s, p, d and f. The maximum number of electrons in these subshells can be calculated by following formula:

2 (2l +1 )

and l = 0,1,2,3,

maximum numbers of electrons in s subshell are,

l=0

2 ( 2(0) + 1)

2

so maximum electrons in s subshell are 2.

maximum numbers of electrons in p subshell are,

l = 1

2 ( 2(1) + 1)

2( 2 + 1

6

so maximum electrons in p subshell are 6.

maximum numbers of electrons in d subshell are,

l = 2

2 ( 2(2) + 1)

2( 4 + 1)

10

so maximum electrons in d subshell are 10.

maximum numbers of electrons in f subshell are,

l = 3

2 ( 2(3) + 1)

2( 6 + 1)

14

so maximum electrons in f subshell are 14.

in 1783 cavendish was working with his hydrogen gas and found that when he burned it and condensed the vapor it was water. this was very significant since it disproved the greek theory of elements completely since water was not a simple substance but the product of two gases. it was lavoisier who hearing of the experiment gave cavendish's gas the name hydrogen ("water-producer") and added that hydrogen burned by combining with oxygen and that water was a hydrogen-oxygen combination.

explanation: