Define neutral atom, element, molecule. 2. Give 3 examples of element, molecule. 3. State the bond found in ZnO, Al2O3, CaCl2. 4. With a diagram, explain the formation of BeCl2.

(a) NaCl

Step 1: Lewis dot symbols of atoms.
Sodium (Group 1): 1 valence electron.
$Na \cdot$
Chlorine (Group 17): 7 valence electrons.
$\cdot \ddot{Cl} \cdot$

Step 2: Electron transfer for octet stability.
Na loses 1 electron to Cl (Na achieves He configuration, Cl achieves octet).
$Na \cdot + \cdot \ddot{Cl} \cdot \ \longrightarrow \ [Na]^{+} + [\ :\!\ddot{Cl}\!:\ ]^{-}$

Step 3: Ionic bond formation.
Oppositely charged ions $[Na]^{+}$ and $[\ :\!\ddot{Cl}\!:\ ]^{-}$ are held by electrostatic attraction.

Final Lewis dot diagram:
[\mathrm{Na]^{+} \ [\ :!\ddot{Cl}!:\ ]^{-}}

(b) MgO

Step 1: Lewis dot symbols of atoms.
Magnesium (Group 2): 2 valence electrons.
$\cdot Mg \cdot$
Oxygen (Group 16): 6 valence electrons.
$\cdot \ddot{O} \cdot$

Step 2: Electron transfer for octet stability.
Mg loses 2 electrons to O (Mg achieves Ne configuration, O achieves octet).
$\cdot Mg \cdot + \cdot \ddot{O} \cdot \ \longrightarrow \ [Mg]^{2+} + [\ :\!\ddot{O}\!:\ ]^{2-}$

Step 3: Ionic bond formation.
Oppositely charged ions $[Mg]^{2+}$ and $[\ :\!\ddot{O}\!:\ ]^{2-}$ are held by electrostatic attraction.

Final Lewis dot diagram:
[\mathrm{Mg]^{2+} \ [\ :!\ddot{O}!:\ ]^{2-}}

(c) CaF₂

Step 1: Lewis dot symbols of atoms.
Calcium (Group 2): 2 valence electrons.
$\cdot Ca \cdot$
Fluorine (Group 17): 7 valence electrons (×2).
$\cdot \ddot{F} \cdot$

Step 2: Electron transfer for octet stability.
Ca loses 2 electrons (1 to each F). Ca achieves Ar configuration, each F achieves octet.
$\cdot Ca \cdot + 2(\cdot \ddot{F} \cdot) \ \longrightarrow \ [Ca]^{2+} + 2[\ :\!\ddot{F}\!:\ ]^{-}$

Step 3: Ionic bond formation.
Oppositely charged ions $[Ca]^{2+}$ and $2[\ :\!\ddot{F}\!:\ ]^{-}$ are held by electrostatic attraction.

Final Lewis dot diagram:
[\mathrm{Ca]^{2+} \ 2[\ :!\ddot{F}!:\ ]^{-}}