Formal Charge vs Oxidation Number Flashcards: Electron Accounting
Practice formal charge vs oxidation number with 48 original English flashcards: bond allocation, single-atom calculations, charge checks, and error repairs.
Mayelana naleli qoqo
Practice formal charge vs oxidation number (oxidation state) with 48 original English flashcards for introductory chemistry learners who can read short Lewis structures.
The cards practice method → electron-allocation rule; a specified structure and target atom → one signed result; a faulty count or label → its repair; atom values and multiplicities → the species total; and a claim or missing input → whether the conclusion is supported. Two selected comparisons ask for formal charge and oxidation number together, for carbon in CO and oxygen in OF2. Other cards distinguish an atom's bookkeeping number from the charge of the whole species or an electron-density-based partial charge.
Six counting anchors come first. Short calculations then mix neutral molecules, ions, single and multiple bonds, and identical-element bonds. Error repairs follow, with related variants separated by at least three unrelated cards. The last part mixes total checks, a specified nitrate resonance form, peroxide and oxygen–fluorine cases, matching numerical answers, and missing-information decisions. Every structure-based calculation supplies its bonds, lone pairs, target, overall charge, and any needed electronegativity order in text; no diagram is required.
This is narrow electron-accounting practice. It excludes number → molecule guessing because one number fits many structures; exhaustive atom and direction permutations; full Lewis-structure drawing, molecule-wide multipart calculations, and redox balancing because they need longer written practice; and radicals, transition-metal coordination chemistry, and complete exam curricula because they exceed this scope. Recall practice should be followed by fresh calculations on paper.
Read the formal charge and oxidation number lesson for a longer explanation, or the chemistry flashcard study guide for practice advice. The accounting conventions are checked against the IUPAC entries for formal charge and oxidation state.
The questions, explanations, selection, and order are independently composed from scientific facts, with AI-assisted drafting and an original AI-generated abstract cover. No textbook, examination, or competitor questions, answers, or figures were copied or adapted. Common knowledge · CC0 1.0 applies to this original expression and media to the extent applicable rights exist; it does not claim ownership of scientific facts or third-party source material. This is an independent study aid with no examination-board or source-publisher affiliation.
Amakhadi akuleli qoqo
Ikhadi 1
Umbuzo
Formal charge: how are a bond's electrons assigned?
Impendulo
Half to each bonded atom, regardless of electronegativity.
Ikhadi 2
Umbuzo
Electron accounting: how many nonbonding electrons are in three lone pairs?
Impendulo
Six electrons. Each lone pair contains two electrons.
Ikhadi 3
Umbuzo
Lewis counting: how many bonding electrons are in a single, double, and triple bond?
Impendulo
Two, four, and six, respectively. Each bond line represents one electron pair.
Ikhadi 4
Umbuzo
Oxidation number: how are electrons allocated in an ordinary bond between different elements?
Impendulo
Assign the entire bonding pair to the more electronegative atom. Nonbonding electrons stay with their atom.
Ikhadi 5
Umbuzo
Electron accounting: what must the sum of all atom formal charges, or all atom oxidation numbers, equal?
Impendulo
The charge of the whole species. For a neutral molecule, each sum is zero.
Ikhadi 6
Umbuzo
Formal charge: what's the calculation for a specified Lewis structure?
Impendulo
Neutral valence electrons − nonbonding electrons − half the bonding electrons. Read the target atom's counts from that particular structure.
Ikhadi 7
Umbuzo
NH4+ (charge +1): four N–H single bonds; no lone pairs on N or H. N formal charge? N has 5 valence electrons.
Impendulo
+1 — N receives 4 bonding electrons: 5 − 0 − 4 = +1.
Ikhadi 8
Umbuzo
Neutral H–F: one single bond; F has 3 lone pairs, H none. F is more electronegative than H. H oxidation number? H has 1 valence electron.
Impendulo
+1 — the bonding pair goes to F, leaving H assigned 0 electrons: 1 − 0 = +1.
Ikhadi 9
Umbuzo
Neutral O=C=O: C has no lone pairs; each O has 2. C formal charge? C has 4 valence electrons.
Impendulo
Zero — two double bonds assign C 4 bonding electrons: 4 − 0 − 4 = 0.
Ikhadi 10
Umbuzo
OH− (charge −1): one O–H single bond; O has 3 lone pairs, H none. O formal charge? O has 6 valence electrons.
Impendulo
−1 — O receives 1 bonding electron: 6 − 6 − 1 = −1.
Ikhadi 11
Umbuzo
Neutral N≡N: each N has 1 lone pair. Either N oxidation number? N has 5 valence electrons.
Impendulo
Zero — each N is assigned 2 nonbonding electrons and 3 bonding electrons: 5 − 2 − 3 = 0.
Ikhadi 12
Umbuzo
Neutral CH3Cl: C has 3 C–H single bonds and 1 C–Cl single bond; C and H have no lone pairs, Cl has 3. Cl > C > H in electronegativity. C oxidation number? C has 4 valence electrons.
Impendulo
−2 — C gets 6 electrons from the C–H bonds and none from C–Cl: 4 − 6 = −2.
Ikhadi 13
Umbuzo
Neutral H–C≡N: N has 1 lone pair; C and H have none. N formal charge? N has 5 valence electrons.
Impendulo
Zero — N receives 3 electrons from the triple bond: 5 − 2 − 3 = 0.
Ikhadi 14
Umbuzo
Neutral H2C=CH2: each C has 2 C–H single bonds and the C=C double bond; no atom has lone pairs. C > H in electronegativity. Either C oxidation number? C has 4 valence electrons.
Impendulo
−2 — C gets 4 electrons from C–H and 2 from half the C=C bond: 4 − 6 = −2.
Ikhadi 15
Umbuzo
CN− (charge −1): C≡N; each atom has 1 lone pair. N is more electronegative than C. C oxidation number? C has 4 valence electrons.
Impendulo
+2 — C keeps only its 2 nonbonding electrons: 4 − 2 = +2.
Ikhadi 16
Umbuzo
Neutral CH3F: four single bonds around C; C and H have no lone pairs, F has 3. F formal charge? F has 7 valence electrons.
Impendulo
Zero — F receives 1 bonding electron: 7 − 6 − 1 = 0.
Ikhadi 17
Umbuzo
Neutral CH3–O–H: all bonds are single; O has 2 lone pairs, C and H none. O formal charge? O has 6 valence electrons.
Impendulo
Zero — O receives 1 electron from each of its two bonds: 6 − 4 − 2 = 0.
Ikhadi 18
Umbuzo
Neutral H2C=O: C has 2 C–H single bonds and 1 C=O double bond; O has 2 lone pairs, C and H none. O > C > H in electronegativity. C oxidation number? C has 4 valence electrons.
Impendulo
Zero — C gets 4 electrons from C–H and none from C=O: 4 − 4 = 0.
Ikhadi 19
Umbuzo
NH2− (charge −1): two N–H single bonds; N has 2 lone pairs, H none. N formal charge? N has 5 valence electrons.
Impendulo
−1 — N receives 2 bonding electrons: 5 − 4 − 2 = −1.
Ikhadi 20
Umbuzo
Neutral H–C≡C–H: no atom has lone pairs. C > H in electronegativity. Either C oxidation number? C has 4 valence electrons.
Impendulo
−1 — C gets 2 electrons from C–H and 3 from half the C≡C bond: 4 − 5 = −1.
Ikhadi 21
Umbuzo
H3O+ (charge +1): three O–H single bonds; O has 1 lone pair, H none. O formal charge? O has 6 valence electrons.
Impendulo
+1 — O receives 3 bonding electrons: 6 − 2 − 3 = +1.
Ikhadi 22
Umbuzo
Neutral F–O–F: both bonds are single; O has 2 lone pairs and each F has 3. O formal charge? O has 6 valence electrons.
Impendulo
Zero — O receives 2 bonding electrons: 6 − 4 − 2 = 0.
Ikhadi 23
Umbuzo
Neutral H2N–NH2: all bonds are single; each N has 1 lone pair, H none. N > H in electronegativity. Either N oxidation number? N has 5 valence electrons.
Impendulo
−2 — N keeps 2 nonbonding electrons, gets 4 from N–H, and 1 from N–N: 5 − 7 = −2.
Ikhadi 24
Umbuzo
Neutral F–F: one single bond; each F has 3 lone pairs. Either F oxidation number? F has 7 valence electrons.
Impendulo
Zero — each F keeps 6 nonbonding electrons and half the bond: 7 − 6 − 1 = 0.
Ikhadi 25
Umbuzo
NH4+ (charge +1): four N–H single bonds, no lone pairs. N > H in electronegativity. Giving N all 8 bonding electrons yields −3. Which accounting label belongs on that result?
Impendulo
Oxidation number. Equal sharing instead gives N formal charge +1: 5 − 4 = +1.
Ikhadi 26
Umbuzo
Neutral H–O–H: O has 2 lone pairs; H none. A formal-charge calculation subtracts 2 for O's nonbonding electrons. What count should replace it?
Impendulo
Four electrons. Two lone pairs contain 4 electrons, so O formal charge is 6 − 4 − 2 = 0.
Ikhadi 27
Umbuzo
Neutral O=C=O: C has no lone pairs; each O has 2. A formal-charge calculation assigns C only 2 bonding electrons because it has two neighbors. What count should replace it?
Impendulo
Four electrons. Each double bond assigns C 2 electrons, giving 4 − 4 = 0.
Ikhadi 28
Umbuzo
Neutral F–F: each F has 3 lone pairs. An oxidation-number calculation gives both bonding electrons to the left F. How should this bond be allocated?
Impendulo
One electron to each F. Identical-element bonds are split equally, so both F oxidation numbers are zero.
Ikhadi 29
Umbuzo
OH− (charge −1): O–H single bond; O has 3 lone pairs, H none. A formal-charge calculation gives O both bonding electrons. How many should O receive?
Impendulo
One bonding electron. Formal charge splits the pair, giving O: 6 − 6 − 1 = −1.
Ikhadi 30
Umbuzo
Neutral H2N–NH2: all bonds single; each N has 1 lone pair, H none. N > H in electronegativity. Does the N–N bond contribute +1 or −1 to either N's oxidation number?
Impendulo
Neither; its contribution is zero. The N–N electrons are shared equally; the two N–H bonds give each N oxidation number −2.
Ikhadi 31
Umbuzo
Neutral H–C≡N: N has 1 lone pair; C and H none. A formal-charge calculation assigns N only 1 electron from C≡N. What count should replace it?
Impendulo
Three electrons. A triple bond contains 6 electrons; N receives half, so 5 − 2 − 3 = 0.
Ikhadi 32
Umbuzo
Neutral F–O–F: O has 2 lone pairs, each F has 3. F > O in electronegativity. A learner uses 'oxygen is always −2.' What is O's oxidation number here?
Impendulo
+2 — both O–F bonding pairs go to F; O keeps 4 electrons: 6 − 4 = +2.
Ikhadi 33
Umbuzo
Neutral CH3–O–H: all bonds single; O has 2 lone pairs, C and H none. O > C > H in electronegativity. A learner copies C's formal charge of zero as its oxidation number. What should C's oxidation number be?
Impendulo
−2 — C gets 6 electrons from its three C–H bonds and none from C–O: 4 − 6 = −2.
Ikhadi 34
Umbuzo
CN− (charge −1): C≡N; each atom has 1 lone pair. N > C in electronegativity. Must C have a negative oxidation number because the ion is negative?
Impendulo
No; C is +2. C keeps 2 nonbonding electrons, while N receives 8 electrons and is −3; +2 − 3 = −1.
Ikhadi 35
Umbuzo
A neutral molecule's atom formal charges add to +1. Can that be a complete, consistent charge assignment?
Impendulo
No. A neutral species requires a total of zero; recheck the counts and any omitted atoms.
Ikhadi 36
Umbuzo
Neutral H–O–O–H: all bonds single; each O has 2 lone pairs, H none. O > H in electronegativity. Either O oxidation number? O has 6 valence electrons.
Impendulo
−1 — O keeps 4 nonbonding electrons, gets 2 from O–H and 1 from O–O: 6 − 7 = −1.
Ikhadi 37
Umbuzo
Neutral O=C=O: C has no lone pairs; each O has 2. O > C in electronegativity. Labels C +4 and each O −2 sum to zero. Does that make them correct formal charges?
Impendulo
No. Those are oxidation numbers; this Lewis structure has formal charge zero on every atom. A correct total doesn't identify the method.
Ikhadi 38
Umbuzo
NO3− (charge −1), one specified resonance form: N=Oa, N–Ob, N–Oc; N has no lone pairs, Oa has 2, Ob and Oc have 3 each. Ob formal charge? O has 6 valence electrons.
Impendulo
−1 — Ob is singly bonded with 6 nonbonding electrons: 6 − 6 − 1 = −1.
Ikhadi 39
Umbuzo
H3O+ (charge +1): three O–H single bonds; O has 1 lone pair, H none. O formal charge is +1 and each H is zero. What is their total?
Impendulo
+1 — add one O and three H: +1 + 3(0) = +1.
Ikhadi 40
Umbuzo
Does an atom's formal charge specify its measured local electric charge inside a molecule?
Impendulo
No. Formal charge follows a counting convention; electron-density-based partial charges require a stated method and are a different quantity.
Ikhadi 41
Umbuzo
CO3²− (charge −2): C oxidation number +4, each of the three O atoms −2. What is the oxidation-number total?
Impendulo
−2 — +4 + 3(−2) = −2, matching the ion charge.
Ikhadi 42
Umbuzo
Only the neutral formula C2H4O2 is supplied. Can it uniquely determine the oxidation number of each individual carbon atom?
Impendulo
No. Connectivity matters: the formula alone doesn't say which bonds belong to each carbon atom.
Ikhadi 43
Umbuzo
Neutral C≡O: each atom has 1 lone pair; O > C in electronegativity. C has 4 valence electrons. C formal charge and oxidation number, respectively?
Impendulo
−1 and +2. Formal charge: 4 − 2 − 3 = −1. Oxidation number: the triple-bond electrons go to O, so 4 − 2 = +2.
Ikhadi 44
Umbuzo
NH4+ has overall charge +1. Does that tell you that every atom has formal charge +1?
Impendulo
No. The +1 is the total for the ion. In its four-single-bond Lewis structure with no lone pairs, N is +1 and each H is zero.
Ikhadi 45
Umbuzo
Neutral H–H: one single bond; no lone pairs. Each H has 1 valence electron. Does H having zero for both formal charge and oxidation number make the two methods interchangeable?
Impendulo
No. Both methods split this identical-element bond equally, but they allocate ordinary different-element bonds differently.
Ikhadi 46
Umbuzo
NO3−: in each of its three equivalent Lewis resonance forms, the O formal charges are 0, −1, and −1. Is −2/3 the formal charge of an O atom in one of those forms?
Impendulo
No. It is the average across equivalent forms; in any specified form an O formal charge is either 0 or −1.
Ikhadi 47
Umbuzo
A prompt gives an atom's element and bond orders but omits its nonbonding electrons and overall species charge. Is that enough to determine its formal charge uniquely?
Impendulo
No. You need the nonbonding-electron count or enough additional information to deduce it.
Ikhadi 48
Umbuzo
Neutral F–O–F: O has 2 lone pairs, each F has 3; F > O in electronegativity. O has 6 valence electrons. O formal charge and oxidation number, respectively?
Impendulo
Zero and +2. Formal charge: 6 − 4 − 2 = 0. Oxidation number: both bonding pairs go to F, so 6 − 4 = +2.
amakhadi angu-48
Formal Charge vs Oxidation Number Flashcards: Electron Accounting
I-Nibomo iyavuleka ukuze uqale ukufunda.