Before we can use this equation for calculations we must first balance it.
What whole number should be placed in the
green box to balance this equation?
2C2H6 + [? ]02 → [ ]CO2 + [ ]H20
Remember, the coefficients should be the
smallest whole numbers possible.

2C₂H₆ +  [7]O₂     →      [4]CO₂ + [6]H₂O

Explanation:

Chemical equation:

C₂H₆ +  O₂     →      CO₂ + H₂O

Balanced chemical equation:

2C₂H₆ +  7O₂     →      4CO₂ + 6H₂O

Step 1:

2C₂H₆ +  O₂     →      CO₂ + H₂O

Left hand side                      Right hand side

C = 4                                     C = 1

H = 12                                    H = 2

O = 2                                     O = 3

Step 2:

2C₂H₆ +  O₂     →      4CO₂ + H₂O

Left hand side                      Right hand side

C = 4                                     C =  4

H = 12                                    H = 2

O = 2                                     O = 9

Step 3:

2C₂H₆ +  O₂     →      4CO₂ + 6H₂O

Left hand side                      Right hand side

C = 4                                     C =  4

H = 12                                    H = 12

O = 2                                     O = 14

Step 4:

2C₂H₆ +  7O₂     →      4CO₂ + 6H₂O

Left hand side                      Right hand side

C = 4                                     C =  4

H = 12                                    H = 12

O = 14                                     O = 14

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.