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VICChemistryQuick questions
Unit 1: How can the diversity of materials be explained?
Quick questions on Covalent bonding, Lewis structures, VSEPR and polarity: VCE Chemistry Unit 1
10short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is covalent bonding?Show answer
A covalent bond is a shared pair of electrons between two non-metal atoms. Each atom contributes one electron to the shared pair. The shared pair is attracted to both nuclei, holding the atoms together.
What is lewis structures?Show answer
A Lewis (electron-dot) structure shows every valence electron as a pair of dots or as a line (for a bonding pair). Procedure:
What is vSEPR theory?Show answer
Valence Shell Electron Pair Repulsion theory states that electron pairs around a central atom repel each other and arrange to maximise their separation. Both bonding pairs and lone pairs count. Multiple bonds count as one electron domain.
What is polarity?Show answer
A bond is polar if the bonded atoms differ in electronegativity. The more electronegative atom carries a partial negative charge and the other a partial positive charge. A common rule of thumb: a difference in Pauling electronegativity of about 0.4 or more produces a noticeably polar bond; about 1.7 or more usually indicates an ionic bond.
What is forgetting lone pairs in the VSEPR count?Show answer
H2O has 4 electron pairs around O, not 2.
What is calling CO2 polar?Show answer
Each C=O is polar, but the two dipoles point opposite ways and exactly cancel. CO2 is non-polar.
What is counting a double bond as 2 electron domains?Show answer
VSEPR counts a multiple bond as a single domain. CO2 has 2 domains around C and is linear.
What is drawing a Lewis structure with the wrong number of electrons?Show answer
Always sum group numbers and adjust for charge before placing electrons.
What is forgetting brackets around an ionic Lewis structure?Show answer
Ions must show the structure in [ ] with the overall charge as a superscript.
What is applying octet rules to H and Be/B?Show answer
Hydrogen wants 2 electrons. Beryllium and boron are commonly stable with 4 and 6, respectively.