A. use the following steps to balance the redox reaction below. al(s) ni2 (aq) ni(s) al3 (aq)
i. write the oxidation and reduction half-reactions. make sure each half-reaction is balanced for number of atoms and charge.
ii. multiply each half-reaction by the correct number in order to balance charges for the two half-reactions.
iii. add the equations and simplify to get a balanced equation.

2Al(s) +3Ni²⁺(aq) ⟶ 2Al³⁺(aq) + 3Ni(s)  

Explanation:

The unbalanced equation is

Al(s) + Ni²⁺(aq) ⟶ Ni(s) + Al³⁺(aq)

(i) Half-reactions

Al(s) ⟶ Al³⁺(aq) + 3e⁻

Ni²⁺(aq) + 2e⁻ ⟶ Ni(s)

(ii) Balance charges

2 × [Al(s) ⟶ Al³⁺(aq) + 3e⁻]

3 × [Ni²⁺(aq) + 2e⁻ ⟶ Ni(s)]

gives

2Al(s) ⟶ 2Al³⁺(aq) + 6e⁻

3Ni²⁺(aq) + 6e⁻ ⟶ 3Ni(s)

(iii) Add equations

2Al(s) ⟶ 2Al³⁺(aq) + 6e⁻

3Ni²⁺(aq) + 6e⁻ ⟶ 3Ni(s)                                        

2Al(s) +3Ni²⁺(aq) + 6e⁻ ⟶ 2Al³⁺(aq) + 3Ni(s) + 6e⁻

Simplify (cancel electrons)

2Al(s) +3Ni²⁺(aq) ⟶ 2Al³⁺(aq) + 3Ni(s)

if two electrons have the same n, the same ℓ, and the same ml, then they are in the same orbital. the pauli exclusion principle states that no two identical fermions (a fancy word for electrons and other subatomic particles like electrons) may occupy the same quantum state in an atom simultaneously.

most historians agree that gabriel mouton, the vicar of st. paul’s church in lyons, france, is the “founding father” of the metric system. he proposed a decimal system of measurement in 1670. mouton based it on the length of one minute of arc of a great circle of the earth (now called a nautical mile, 1852 meters). he also proposed the swing-length of a pendulum with a frequency of one beat per second as the unit of length (about 25 cm). a pendulum beating with this length would have been fairly easy to produce, thus facilitating the widespread distribution of uniform standards. over the years, his work was revised, improved, and extended by a number of french scientists.

the political sponsor of weights and measures reform in the french revolutionary national assembly was the bishop of autun, better known as talleyrand. under his auspices, the french academy appointed several committees to carry out the work of developing a usable system of weights and measures for france. one of the committees recommended a decimalized measurement system based upon a length equal to one ten-millionth of the length of a quadrant of the earth’s meridian (i.e., one ten-millionth of the distance between the equator and the north pole).