Valence Electrons and Ionic Compounds - AP Chemistry

1. How many valence electrons does aluminum have?

   3 valence electrons. Group 13 elements have 3 valence electrons.

2. What is the valence electron configuration for nitrogen?

   $2s^2 2p^3$. Second shell configuration for nitrogen.

3. How many electrons does a chloride ion have?

   18 electrons. Neutral Cl has 17; Cl$^-$ gains 1 electron.

4. What is the electron configuration for a potassium ion?

   $1s^2 2s^2 2p^6 3s^2 3p^6$. K$^+$ has same configuration as argon.

5. Identify the number of valence electrons in helium.

   2 valence electrons. Noble gas with complete outer shell.

6. What is the chemical formula for calcium fluoride?

   CaF$_2$. One Ca$^{2+}$ balances two F$^-$ charges.

7. What is the formula for the compound formed by Al and O?

   Al$_2$O$_3$. Balances two +3 charges with three -2 charges.

8. Predict the formula of the compound formed by Mg and Cl.

   MgCl$_2$. Balances +2 charge with two -1 charges.

9. What is the formula for the compound formed by Na and S?

   Na$_2$S. Two Na$^+$ balance one S$^{2-}$ charge.

10. What is the formula for the compound formed by K and Br?

    KBr. 1:1 ratio balances +1 and -1 charges.

11. State the number of valence electrons in fluorine.

    7 valence electrons. Group 17 elements have 7 valence electrons.

12. What is the charge of a sodium ion?

    +1. Na loses 1 electron to achieve stable octet.

13. What is the chemical symbol for a sodium ion?

    Na$^+$. Symbol shows +1 charge from electron loss.

14. What is the typical charge on an oxide ion?

    -2. O gains 2 electrons to complete octet.

15. What is the electron configuration of a fluoride ion?

    $1s^2 2s^2 2p^6$. F$^-$ gains electron to match neon configuration.

16. How many valence electrons are in sulfur?

    6 valence electrons. Group 16 elements have 6 valence electrons.

17. What is the charge on a phosphide ion?

    -3. P gains 3 electrons to achieve octet.

18. How many valence electrons does argon have?

    8 valence electrons. Noble gas with complete outer shell.

19. What is the typical charge of a barium ion?

    +2. Ba loses 2 electrons for stable configuration.

20. What is the electron configuration for a magnesium ion?

    $1s^2 2s^2 2p^6$. Mg$^{2+}$ has same configuration as neon.

21. How many valence electrons does carbon have?

    4 valence electrons. Group 14 elements have 4 valence electrons.

22. How many valence electrons does neon have?

    8 valence electrons. Noble gas with complete outer shell.

23. Determine the valence electron count for phosphorus.

    5 valence electrons. Group 15 elements have 5 valence electrons.

24. How many valence electrons are in boron?

    3 valence electrons. Group 13 elements have 3 valence electrons.

25. Identify the number of valence electrons in chlorine.

    7 valence electrons. Group 17 elements have 7 valence electrons.

26. Identify the typical ionic charge for a calcium ion.

    +2. Ca loses 2 electrons for stable configuration.

27. State the octet rule.

    Atoms tend to have 8 electrons in their valence shell. Stable electron configuration for most elements.

28. What is the electron configuration of an oxide ion?

    $1s^2 2s^2 2p^6$. O$^{2-}$ has same configuration as neon.

29. What is the definition of valence electrons?

    Electrons in the outermost shell of an atom. These determine chemical bonding and reactivity.

30. What is the charge of a magnesium ion?

    +2. Mg loses 2 electrons for stable octet.

31. How many valence electrons does oxygen have?

    6 valence electrons. Group 16 elements have 6 valence electrons.

32. What is the chemical formula for lithium oxide?

    Li$_2$O. Two Li$^+$ balance one O$^{2-}$ charge.

33. Which type of bond forms between sodium and chlorine?

    Ionic bond. Metal transfers electron to nonmetal.

34. What is the valence electron configuration of argon?

    $3s^2 3p^6$. Third shell configuration for argon.

35. How many electrons does an oxide ion have?

    10 electrons. Neutral O has 8; O$^{2-}$ gains 2 electrons.

36. What is the formula for the compound formed by Ca and Cl?

    CaCl$_2$. One Ca$^{2+}$ balances two Cl$^-$ charges.

37. What is the charge of an aluminum ion?

    +3. Al loses 3 electrons to achieve octet.

38. What charge does a chloride ion have?

    -1. Cl gains 1 electron to complete octet.

39. Identify the charge on a sulfide ion.

    -2. S gains 2 electrons to achieve octet.

40. What is the typical charge on a nitride ion?

    -3. N gains 3 electrons to complete octet.

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