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.

Sodium (Group 1): 1 valence electron.

$$\mathrm{Na \cdot}$$

Chlorine (Group 17): 7 valence electrons.

$$\cdot \ddot{\mathrm{Cl}} \cdot$$

Na loses 1 electron to Cl (Na achieves He configuration, Cl achieves octet).

$$\mathrm{Na \cdot} + \cdot \ddot{\mathrm{Cl}} \cdot \ \longrightarrow \ [\mathrm{Na}]^{+} + [\ :\!\ddot{\mathrm{Cl}}\!:\ ]^{-}$$

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

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

Magnesium (Group 2): 2 valence electrons.

$$\cdot \mathrm{Mg} \cdot$$

Oxygen (Group 16): 6 valence electrons.

$$\cdot \ddot{\mathrm{O}} \cdot$$

Mg loses 2 electrons to O (Mg achieves Ne configuration, O achieves octet).

$$\cdot \mathrm{Mg} \cdot + \cdot \ddot{\mathrm{O}} \cdot \ \longrightarrow \ [\mathrm{Mg}]^{2+} + [\ :\!\ddot{\mathrm{O}}\!:\ ]^{2-}$$

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

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

Calcium (Group 2): 2 valence electrons.

$$\cdot \mathrm{Ca} \cdot$$

Fluorine (Group 17): 7 valence electrons (×2).

$$\cdot \ddot{\mathrm{F}} \cdot$$

Ca loses 2 electrons (1 to each F). Ca achieves Ar configuration, each F achieves octet.

$$\cdot \mathrm{Ca} \cdot + 2(\cdot \ddot{\mathrm{F}} \cdot) \ \longrightarrow \ [\mathrm{Ca}]^{2+} + 2[\ :\!\ddot{\mathrm{F}}\!:\ ]^{-}$$

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

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