Shared pairs: hydrogen, chlorine, oxygen and nitrogen
| English | 中文 | Pinyin |
|---|---|---|
| covalent bond/ˈkəʊvələnt bɒnd/ | 共价键 | gòng jià jiàn |
| lone pair/ləʊn peə/ | 孤对电子 | gū duì diàn zi |
What would explain this observation?
- An oxygen molecule contains two shared electron pairs, while nitrogen contains three. Counting shared pairs distinguishes a double from a triple covalent bond 共价键.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- A covalent bond forms when atoms share a pair of electrons, attracted to both positive nuclei. Hydrogen atoms each contribute one electron to H₂, giving one shared pair and a full first shell of two. Chlorine atoms each have seven outer electrons: in Cl₂ they share one pair and each retains three lone pairs 孤对电子. In HCl, hydrogen and chlorine share one pair; hydrogen has two electrons in its shell and chlorine an octet.
- covalent bond: A bond formed by a shared pair of electrons attracted to both nuclei; lone pair: A pair of outer electrons not shared in a covalent bond.
How many shared pairs join the two nitrogen atoms in N₂?
Oxygen has six outer electrons, so O₂ has two shared pairs, a double bond, and two lone pairs on each atom. Nitrogen has five outer electrons, so N₂ has three shared pairs, a triple bond, and one lone pair on each atom. A line diagram writes H–H, Cl–Cl, H–Cl, O=O or N≡N. One line represents one shared pair, not one electron.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Oxygen has six outer electrons, so O₂ has two shared pairs, a double bond, and two lone pairs on each atom. Nitrogen has five outer electrons, so N₂ has three shared pairs, a triple bond, and one lone pair on each atom. A line diagram writes H–H, Cl–Cl, H–Cl, O=O or N≡N. One line represents one shared pair, not one electron.
- Count the available outer electrons first. Place shared pairs between the correct atoms using dots from one and crosses from the other, then place remaining electrons as lone pairs. Check each atom’s full outer shell and the total electrons drawn. Compare with a line or ball-and-stick model: these make connectivity clear but normally omit lone pairs and electron origin.
Which two habits make the investigation or model in this case more defensible?
Count the available outer electrons first. Place shared pairs between the correct atoms using dots from one and crosses from the other, then place remaining electrons as lone pairs. Check each atom’s full outer shell and the total electrons drawn. Compare with a line or ball-and-stick model: these make connectivity clear but normally omit lone pairs and electron origin.
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: O₂ has 2×6=12 outer electrons altogether. Four are in its two shared pairs; the remaining eight form four lone pairs, two on each oxygen. Each oxygen counts the four shared electrons plus its own four unshared electrons as an octet. Shared electrons are counted by both atoms for shell completion but drawn only once in the molecule.
How many shared electrons are present in the double bond of O₂? Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
How many shared electrons are present in the double bond of O₂?
The result is 4 electrons. Known: O₂ has 2×6=12 outer electrons altogether. Four are in its two shared pairs; the remaining eight form four lone pairs, two on each oxygen. Each oxygen counts the four shared electrons plus its own four unshared electrons as an octet. Shared electrons are counted by both atoms for shell completion but drawn only once in the molecule.
Check the conclusion and its limits
- A double bond contains four shared electrons, not two. A chlorine atom’s six unshared electrons must not disappear just because a line diagram omits them. These simple electron pictures are models, not a claim that electron positions are fixed dots or that a bond is a literal rod.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Each line in a displayed formula represents only one electron. This claim is false: A double bond contains four shared electrons, not two. A chlorine atom’s six unshared electrons must not disappear just because a line diagram omits them. These simple electron pictures are models, not a claim that electron positions are fixed dots or that a bond is a literal rod.
Shared pairs: hydrogen, chlorine, oxygen and nitrogen: Oxygen has six outer electrons, so O₂ has two shared pairs, a double bond, and two lone pairs on each atom. Nitrogen has five outer electrons, so N₂ has three shared pairs, a triple bond, and one lone pair on each atom. A line diagram writes H–H, Cl–Cl, H–Cl, O=O or N≡N. One line represents one shared pair, not one electron.
Each line in a displayed formula represents only one electron.
A double bond contains four shared electrons, not two. A chlorine atom’s six unshared electrons must not disappear just because a line diagram omits them. These simple electron pictures are models, not a claim that electron positions are fixed dots or that a bond is a literal rod.
A bond formed by a shared pair of electrons attracted to both nuclei: write the technical term.
covalent bond means A bond formed by a shared pair of electrons attracted to both nuclei.