9.a) Sodium (Na) has an electron configuration of 2, 8, 1. Chlorine (Cl) has an electron configuration of 2, 8, 7. Sodium transfers its single valence electron to chlorine, forming a positive sodium ion (Na$^+$) and a negative chloride ion (Cl$^-$). The electrostatic attraction between these oppositely charged ions forms an ionic bond. $$ \text{Na} \cdot \quad + \quad \text{:} \ddot{\text{Cl}} \text{:} \quad \longrightarrow \quad [\text{Na}]^+ \quad [\text{:} \ddot{\text{Cl}} \text{:} \text{.} ]^- $$ (The dot represents the electron from sodium, and the crosses represent electrons from chlorine.) 9.b) Two apparatus used for measuring exact volumes of solutions in the laboratory are: 1. Burette Drawing description: A long, narrow glass tube with precise volume markings (graduations) along its length and a stopcock at the bottom to control the flow of liquid. It is typically held vertically by a clamp and stand. 2. Pipette (specifically a volumetric or transfer pipette) Drawing description: A long, slender glass tube with a bulb in the middle and a single calibration mark (fiducial mark) indicating a specific, fixed volume. It is used with a pipette filler to draw liquid up to the mark. 3 done, 2 left today. You're making progress.