Question

proposed lewis structure is the proposed lewis structure reasonable? yes. no, it has the wrong number of valence electrons. the correct number is: no, it has the right number of valence electrons but doesnt satisfy the octet rule. the symbols of the problem atoms are: yes. no, it has the wrong number of valence electrons. the correct number is: no, it has the right number of valence electrons but doesnt satisfy the octet rule. the symbols of the problem atoms are: yes. no, it has the wrong number of valence electrons. the correct number is: no, it has the right number of valence electrons but doesnt satisfy the octet rule. the symbols of the problem atoms are: if two or more atoms of the same element dont satisfy the octet rule, just enter the chemical symbol as many times as necessary. for example, if two oxygen atoms dont satisfy the octet rule, enter \o o\.

Explanation:

Step1: Calculate valence electrons for \(FO_2\)

F has 7 valence electrons, O has 6 valence electrons. Total valence electrons \(=7 + 6\times2=19\). In the proposed structure \(:F = O = F:\), each F has 8 electrons (octet), O has 8 electrons (octet). But F - O double bond is not typical (F usually forms single bonds). However, let's check valence electrons. Each F has 6 non - bonding electrons and 2 in the double bond (\(6 + 2=8\)), O has 4 non - bonding electrons and 4 in double bonds (\(4+4 = 8\)). The total number of valence electrons in the structure is \(6\times2+4+2\times2=20\). The correct number of valence electrons for \(FO_2\) (assuming it exists as a neutral species, though it's a bit of a stretch as \(OF_2\) is more common with \(O - F\) single bonds) is \(7+6\times2 = 19\). But if we consider formal charges and more stable bonding, F should form single bonds. But if we just count valence electrons in the structure:
- Each F has 6 non - bonding electrons and 2 in the double bond (\(6 + 2=8\)), O has 4 non - bonding electrons and 4 in double bonds (\(4 + 4=8\)). The total number of valence electrons in the structure is \(6\times2+4+2\times2=20\). The correct number of valence electrons for \(FO_2\) (if we assume the formula is \(O_2F\)): \(O\) has 6 valence electrons, \(F\) has 7. \(6\times2+7=19\). So it has the wrong number of valence electrons.

Step2: Calculate valence electrons for \(N_2\)

N has 5 valence electrons. For \(N_2\), the correct Lewis structure is \(N\equiv N\). In the proposed structure \(N - N\) (single bond), each N has 6 non - bonding electrons and 2 in the single bond (\(6+2 = 8\)) in terms of electron count, but the number of valence electrons in the proposed structure: \(6\times2+2=14\). The correct number of valence electrons for \(N_2\) is \(5\times2=10\). The structure \(N - N\) is wrong because of the wrong number of valence electrons.

Step3: Calculate valence electrons for \([CN]^{-}\)

C has 4 valence electrons, N has 5 valence electrons, and there is an extra electron due to the negative charge. Total valence electrons \(=4 + 5+1=10\). In the proposed structure \([C = N]^{-}\), C has 4 non - bonding electrons and 4 in the double bond (\(4+4 = 8\)), N has 4 non - bonding electrons and 4 in the double bond (\(4+4=8\)). The total number of valence electrons in the structure is \(4 + 4+4+4 - 1\) (accounting for the negative charge) \(=15\) (wrong). The correct Lewis structure is \([C\equiv N]^{-}\) with \(C\) having 2 non - bonding electrons and 6 in the triple bond (\(2+6 = 8\)), N has 2 non - bonding electrons and 6 in the triple bond (\(2+6=8\)). The number of valence electrons for \([C\equiv N]^{-}\) is \(2+6+2+6 - 1=15\) (wait, no. Let's do it properly. \(C\) in \(C\equiv N\) has 2 non - bonding electrons (lone pair) and 6 in the triple bond (\(3\) bonds, \(2\) electrons per bond). \(N\) has 2 non - bonding electrons and 6 in the triple bond. Plus the extra electron for the negative charge. \(2+6+2+6+1 = 17\) (no). Wait, formula for valence electrons: \(C\) (4) \(+N\) (5) \(+1\) (charge) \(=10\). The correct Lewis structure \([C\equiv N]^{-}\): \(C\) has 2 non - bonding electrons and 6 in the triple bond (\(2 + 6=8\)), \(N\) has 2 non - bonding electrons and 6 in the triple bond (\(2+6 = 8\)). The number of valence electrons: \(2+6+2+6 - 1\) (no, better way: each bond has 2 electrons. Triple bond has 6 electrons. \(C\) has 2 non - bonding electrons (1 lone pair), \(N\) has 2 non - bonding electrons (1 lone pair). Total valence electrons \(=2 + 6+2+6+1\) (charge) \(=17\) (wrong). Wait, no. Valence electrons: \(C\) (4) \(+N\) (5) \(+1\) (charge) \(=10\). In \([C\equiv N]^{-}\), using the formula \(V = NBE+BE\) (where \(V\) is valence electrons, \(NBE\) is non - bonding electrons, \(BE\) is bonding electrons). For \(C\): \(NBE = 2\), \(BE=6\); for \(N\): \(NBE = 2\), \(BE = 6\). \(V=2 + 6+2+6+1\) (charge) \(=17\) (wrong). Wait, no. The formula \(V=\sum_{i}V_i+q\) (\(V_i\) is valence electrons of atom \(i\), \(q\) is charge). \(V = 4+5+( - 1)=8\) (no, \(C\) has 4, \(N\) has 5, charge is \(- 1\). \(4 + 5-1=8\). In \([C\equiv N]^{-}\), \(C\) has 2 non - bonding electrons (\(1\) lone pair) and 6 in the triple bond (\(3\) bonds, \(2\) electrons per bond). \(N\) has 2 non - bonding electrons (\(1\) lone pair) and 6 in the triple bond. \(2+6+2+6=16\) (wrong). Wait, no. Let's use another approach. The octet rule: each atom should have 8 electrons. \(C\) in \([C\equiv N]^{-}\): \(2\) non - bonding (\(1\) lone pair) and \(6\) in bonds (\(3\) bonds). \(N\): \(2\) non - bonding (\(1\) lone pair) and \(6\) in bonds. Total valence electrons \(= (2 + 6)+(2 + 6)-1\) (charge) \(=15\) (wrong). Wait, the correct way: \(C\) has 4 valence electrons, \(N\) has 5, charge is \(-1\). Total valence electrons \(=4 + 5+1=10\). In \([C\equiv N]^{-}\), bonding electrons \(=6\) (triple bond), non - bonding electrons: \(C\) has 2 (\(1\) lone pair), \(N\) has 2 (\(1\) lone pair). \(6+2 + 2=10\). The proposed \([C = N]^{-}\) (double bond): bonding electrons \(=4\), non - bonding electrons: \(C\) has 4, \(N\) has 4. \(4+4+4=12\) (wrong number of valence electrons).

Answer:

• For \(:F = O = F:\): No, it has the wrong number of valence electrons. The correct number is \(19\).
• For \(N - N\): No, it has the wrong number of valence electrons. The correct number is \(10\).
• For \([C = N]^{-}\): No, it has the wrong number of valence electrons. The correct number is \(10\).