Ionic dot-and-cross diagrams: transferred electrons and charges
| English | Français |
|---|---|
| dot-and-cross diagram/dɒt ænd krɒs ˈdaɪəɡræm/ | diagramme point et croix |
| electron transfer/ɪˈlektrɒn ˈtrænsfɜː/ | transfert d'électrons |
What would explain this observation?
- Magnesium loses two electrons while oxygen gains two. A correct diagram shows both the transferred electrons and the final ion charges; a picture of neutral atoms is only the starting point.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Group 1 metals form +1 ions and Group 2 metals +2 ions by losing their outer electrons. Group 7 non-metals gain one electron to form −1 ions, and Group 6 non-metals gain two to form −2 ions. In the specified examples these ions have a noble-gas electronic structure. Magnesium changes from 2,8,2 to Mg²⁺ with 2,8; oxygen changes from 2,6 to O²⁻ with 2,8.
- dot-and-cross diagram 点叉图: An electron diagram using different marks to show the origins of electrons; electron transfer 电子转移: Movement of electrons from one atom to another when ions form.
What belongs in a final MgCl₂ outer-electron diagram?
Draw final ions in separate square brackets, with charges outside. A dot-and-cross diagram uses different marks for electrons originating from different atoms; transferred electrons keep their original marks. Mg²⁺ has no electrons left in its original third shell, while O²⁻ has six original outer electrons plus two transferred ones. If only outer electrons are shown, state whether the remaining filled shell of the cation is omitted by that convention.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Draw final ions in separate square brackets, with charges outside. A dot-and-cross diagram uses different marks for electrons originating from different atoms; transferred electrons keep their original marks. Mg²⁺ has no electrons left in its original third shell, while O²⁻ has six original outer electrons plus two transferred ones. If only outer electrons are shown, state whether the remaining filled shell of the cation is omitted by that convention.
- Start from neutral structures and account for every transferred electron. For NaCl transfer one; for MgO transfer two; for MgCl₂ transfer one to each of two chlorine atoms; for Na₂O transfer one from each of two sodium atoms to oxygen. Confirm total charge zero and outer-shell completion. Dots and crosses indicate origin only: all electrons have the same physical charge and properties.
Which two habits make the investigation or model in this case more defensible?
Start from neutral structures and account for every transferred electron. For NaCl transfer one; for MgO transfer two; for MgCl₂ transfer one to each of two chlorine atoms; for Na₂O transfer one from each of two sodium atoms to oxygen. Confirm total charge zero and outer-shell completion. Dots and crosses indicate origin only: all electrons have the same physical charge and properties.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: MgCl₂ contains one Mg²⁺ and two Cl⁻ ions. Magnesium loses two electrons, one accepted by each chlorine. Charges total +2+2(−1)=0. Each chloride has seven original outer electrons and one transferred electron. The simplest ion ratio is 1:2; the diagram must contain both chloride ions.
How many electrons are transferred when five Mg atoms each form Mg²⁺? Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
How many electrons are transferred when five Mg atoms each form Mg²⁺?
The result is 10 electrons. Known: MgCl₂ contains one Mg²⁺ and two Cl⁻ ions. Magnesium loses two electrons, one accepted by each chlorine. Charges total +2+2(−1)=0. Each chloride has seven original outer electrons and one transferred electron. The simplest ion ratio is 1:2; the diagram must contain both chloride ions.
Check the conclusion and its limits
- An ion has the same proton number as its original atom. Do not write Na²⁺ just because two sodium ions appear, or put the transferred electron halfway between final ions as though it were covalently shared. A full shell in these ion examples does not change the element into the noble gas.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Dots and crosses represent electrons with different electrical charges. This claim is false: An ion has the same proton number as its original atom. Do not write Na²⁺ just because two sodium ions appear, or put the transferred electron halfway between final ions as though it were covalently shared. A full shell in these ion examples does not change the element into the noble gas.
Ionic dot-and-cross diagrams: transferred electrons and charges: Draw final ions in separate square brackets, with charges outside. A dot-and-cross diagram uses different marks for electrons originating from different atoms; transferred electrons keep their original marks. Mg²⁺ has no electrons left in its original third shell, while O²⁻ has six original outer electrons plus two transferred ones. If only outer electrons are shown, state whether the remaining filled shell of the cation is omitted by that convention.
Dots and crosses represent electrons with different electrical charges.
An ion has the same proton number as its original atom. Do not write Na²⁺ just because two sodium ions appear, or put the transferred electron halfway between final ions as though it were covalently shared. A full shell in these ion examples does not change the element into the noble gas.
An electron diagram using different marks to show the origins of electrons: write the technical term.
dot-and-cross diagram means An electron diagram using different marks to show the origins of electrons.