Question

5 calcium fluoride
6 lithium oxide
explain:
choose one compound above and explain how you knew how many ions were needed.

section c

compound name formula total + charge total – charge

7 aluminum oxide
8 aluminum nitride
9 aluminum sulfide
pattern observation:
what do you notice about aluminum compounds and their formulas?

section d
write the ion charges before building the compound.

1. calcium and nitrogen

• calcium charge:
• nitrogen charge:
• final formula:

1. magnesium and oxygen

• magnesium charge:
• oxygen charge:
• final formula:

Explanation:

Step1: Write CaF₂ formula (5)

Calcium ($\text{Ca}^{2+}$), Fluoride ($\text{F}^-$). Balance charge: $2+ + 2(1-) = 0$, so formula $\text{CaF}_2$

Step2: Write Li₂O formula (6)

Lithium ($\text{Li}^+$), Oxide ($\text{O}^{2-}$). Balance charge: $2(1+) + 2- = 0$, so formula $\text{Li}_2\text{O}$

Step3: Explain ion count (CaF₂)

Calcium has $2+$ charge, fluoride $1-$. Need 2 $\text{F}^-$ to cancel $1$ $\text{Ca}^{2+}$ charge, so 1 cation, 2 anions.

Step4: Write Al₂O₃ formula (7)

Aluminum ($\text{Al}^{3+}$), Oxide ($\text{O}^{2-}$). Balance charge: $2(3+) + 3(2-) = 0$, formula $\text{Al}_2\text{O}_3$. Total + charge: $2 \times 3 = +6$, Total - charge: $3 \times 2 = -6$

Step5: Write AlN formula (8)

Aluminum ($\text{Al}^{3+}$), Nitride ($\text{N}^{3-}$). Balance charge: $3+ + 3- = 0$, formula $\text{AlN}$. Total + charge: $+3$, Total - charge: $-3$

Step6: Write Al₂S₃ formula (9)

Aluminum ($\text{Al}^{3+}$), Sulfide ($\text{S}^{2-}$). Balance charge: $2(3+) + 3(2-) = 0$, formula $\text{Al}_2\text{S}_3$. Total + charge: $2 \times 3 = +6$, Total - charge: $3 \times 2 = -6$

Step7: Aluminum compound pattern

Aluminum always forms $\text{Al}^{3+}$; formulas use subscripts to balance this $3+$ charge with the anion's negative charge, resulting in neutral compounds.

Step8: Calcium & Nitrogen ions/formula

Calcium charge: $+2$, Nitrogen (nitride) charge: $-3$. Balance charge: $3(2+) + 2(3-) = 0$, formula $\text{Ca}_3\text{N}_2$

Step9: Magnesium & Oxygen ions/formula

Magnesium charge: $+2$, Oxygen (oxide) charge: $-2$. Balance charge: $2+ + 2- = 0$, formula $\text{MgO}$

(Calcium fluoride): Calcium forms a $2+$ ion, while fluoride forms a $1-$ ion. To make the compound neutral, two $1-$ fluoride ions are needed to balance the single $2+$ calcium ion, resulting in a 1:2 ratio of cations to anions.

Section C:

#	Compound Name	Formula	Total + Charge	Total - Charge
8	Aluminum nitride	$\text{AlN}$	$+3$	$-3$
9	Aluminum sulfide	$\text{Al}_2\text{S}_3$	$+6$	$-6$

Pattern Observation: Aluminum consistently forms a $3+$ cation in these compounds. The subscripts in each formula are chosen to balance this $3+$ charge with the negative charge of the anion, ensuring the overall compound is electrically neutral.

Section D:

1. Calcium and Nitrogen

• Calcium charge: $+2$
• Nitrogen charge: $-3$
• Final formula: $\text{Ca}_3\text{N}_2$

1. Magnesium and Oxygen

• Magnesium charge: $+2$
• Oxygen charge: $-2$
• Final formula: $\text{MgO}$

Answer:

Top Compounds & Explanation:

1. Calcium fluoride: $\text{CaF}_2$
2. Lithium oxide: $\text{Li}_2\text{O}$