Two subatomic particles and their respective electric charges are:

a)

(i) Two subatomic particles and their respective electric charges are:

• Proton: Has a charge of $\boxed{+1}$.
• Electron: Has a charge of $\boxed{-1}$.

b)

(i) For $\text{H}_2\text{SO}_4$:
Number of H atoms = 2
Number of S atoms = 1
Number of O atoms = 4
Total number of atoms (atomicity) = $2 + 1 + 4 = \boxed{7}$

(ii) For $\text{NH}_4\text{OH}$:
Number of N atoms = 1
Number of H atoms = 4 (in $\text{NH}_4$) + 1 (in OH) = 5
Number of O atoms = 1
Total number of atoms (atomicity) = $1 + 5 + 1 = \boxed{7}$

c)

(i) The Aufbau principle states that electrons fill atomic orbitals of the lowest available energy levels before occupying higher energy levels.

(ii)

1. For $\text{Cl}_{17}$ (Chlorine): Electronic configuration: $\boxed{1s^2 2s^2 2p^6 3s^2 3p^5}$ Period: The highest principal quantum number is 3, so it is in Period 3. Group: It has $2+5=7$ valence electrons in the $3s$ and $3p$ orbitals, so it is in Group 17 (or VIIA).

2. For $\text{Mg}_{12}$ (Magnesium): Electronic configuration: $\boxed{1s^2 2s^2 2p^6 3s^2}$ Period: The highest principal quantum number is 3, so it is in Period 3. Group: It has 2 valence electrons in the $3s$ orbital, so it is in Group 2 (or IIA).

d)

(i) $2\text{Na} + \text{Cl}_2 \longrightarrow 2\text{NaCl}$
This is a combination reaction (or synthesis reaction), where two or more reactants combine to form a single product.

(ii) $2\text{H}_2\text{O}_2 \longrightarrow 2\text{H}_2\text{O} + \text{O}_2$
This is a decomposition reaction, where a single compound breaks down into two or more simpler substances.