Answer : The balanced two-half reactions will be,
Oxidation half reaction (anode) : 
Reduction half reaction (cathode) : 
Thus the overall reaction will be,
Explanation :
Voltaic cell : It is defined as a device which is used for the conversion of the chemical energy produces in a redox reaction into the electrical energy. It is also known as the galvanic cell or electrochemical cell.
The given redox reaction occurs between the magnesium and cadmium.
In the voltaic cell, the oxidation occurs at an anode which is a negative electrode and the reduction occurs at the cathode which is a positive electrode.
The balanced two-half reactions will be,
Oxidation half reaction (anode) :
Reduction half reaction (cathode) :
Thus the overall reaction will be,
Remember Coulomb's law: the magnitude of the electric force F between two stationary charges q₁ and q₂ over a distance r is
where k ≈ 8,98 × 10⁹ kg•m³/(s²•C²) is Coulomb's constant.
8.1. The diagram is simple, since only two forces are involved. The particle at Q₂ feels a force to the left due to the particle at Q₁ and a downward force due to the particle at Q₃.
8.2. First convert everything to base SI units:
0,02 µC = 0,02 × 10⁻⁶ C = 2 × 10⁻⁸ C
0,03 µC = 3 × 10⁻⁸ C
0,04 µC = 4 × 10⁻⁸ C
300 mm = 300 × 10⁻³ m = 0,3 m
600 mm = 0,6 m
Force due to Q₁ :
Force due to Q₃ :
8.3. The net force on the particle at Q₂ is the vector
Its magnitude is
and makes an angle θ with the positive horizontal axis (pointing to the right) such that
where we subtract 180° because 
terminates in the third quadrant, but the inverse tangent function can only return angles between -90° and 90°. We use the fact that tan(x) has a period of 180° to get the angle that ends in the right quadrant.
The answer is C. ionic compounds, compared to another hard compound which is the covalent bond, the structure of the ionic compound is lattice or crystalline in form thus less room for imperfections on its structure compared to the latter choices.
The gravity is pushing rhe boat down
