Step 1: Understanding the Concept:
Ionic compounds are typically formed between metals (which tend to lose electrons to form positive ions, cations) and non-metals (which tend to gain electrons to form negative ions, anions). We need to identify which of the given elements are metals and which are non-metals, and then count the possible combinations.
Step 2: Key Formula or Approach:
1. Identify each element from its atomic number.
2. Classify each element as a metal or a non-metal.
3. Determine the stable ion each element typically forms.
4. Count the number of possible pairings between a metal cation and a non-metal anion.
Step 3: Detailed Explanation:
1. Identify the Elements and their Ions:
Z = 8: Oxygen (O), a non-metal. It is in Group 16 and typically forms the anion O$^{2-}$.
Z = 9: Fluorine (F), a non-metal. It is in Group 17 and typically forms the anion F$^{-}$.
Z = 11: Sodium (Na), a metal. It is in Group 1 and typically forms the cation Na$^{+}$.
Z = 19: Potassium (K), a metal. It is in Group 1 and typically forms the cation K$^{+}$.
Z = 20: Calcium (Ca), a metal. It is in Group 2 and typically forms the cation Ca$^{2+}$.
2. List Metals and Non-metals:
Metals (Cation formers): Na, K, Ca
Non-metals (Anion formers): O, F
3. Count the possible combinations:
We pair each metal with each non-metal.
Combinations with Sodium (Na$^{+}$):
1. Na$^{+}$ and F$^{-}$ form NaF.
2. Na$^{+}$ and O$^{2-}$ form Na$_2$O.
Combinations with Potassium (K$^{+}$):
3. K$^{+}$ and F$^{-}$ form KF.
4. K$^{+}$ and O$^{2-}$ form K$_2$O.
Combinations with Calcium (Ca$^{2+}$):
5. Ca$^{2+}$ and F$^{-}$ form CaF$_2$.
6. Ca$^{2+}$ and O$^{2-}$ form CaO.
There are a total of 3 metals and 2 non-metals, leading to $3 \times 2 = 6$ possible ionic compounds.
Step 4: Final Answer:
There are 6 possible ionic compounds that can be formed from the given elements. Therefore, option (A) is correct.