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. That's 2 down. 3 left today — send the next one.