A carbon atom that forms four single covalent bonds (sp3 hybridised), as seen in methane, has which type of molecular geometry around it?
The question asks about the molecular geometry around a carbon atom that forms four single covalent bonds and is sp3 hybridized, using methane as an example. To determine the molecular geometry, we need to consider the VSEPR (Valence Shell Electron Pair Repulsion) theory, which predicts the geometry based on minimizing repulsion between electron pairs around the central atom.
B) Tetrahedral — A carbon atom forming four single covalent bonds (sp3 hybridized) like in methane has four electron domains (all bonding pairs) around it. According to VSEPR theory, this arrangement results in a tetrahedral molecular geometry, with bond angles of approximately \(109.5^\circ\).
In ethene (CH2=CH2), each carbon atom involved in the double bond is best described as:
sp2 hybridised with trigonal planar geometry
Not hybridised at all
sp3 hybridised with tetrahedral geometry
sp hybridised with linear geometry
To determine the hybridization and geometry of carbon atoms in ethene, we need to analyze the bonding around each carbon atom, specifically the number of sigma bonds and lone pairs. The presence of a double bond is a key indicator.
A) sp2 hybridised with trigonal planar geometry — As determined in the step-by-step analysis, each carbon atom in ethene forms three sigma bonds and has no lone pairs, leading to \(\text{sp}^2\) hybridization and a trigonal planar geometry.
In ethyne (HC≡CH), each carbon atom involved in the triple bond is best described as:
sp2 hybridised with trigonal planar geometry
Not hybridised at all
sp hybridised with linear geometry
sp3 hybridised with tetrahedral geometry
To determine the hybridisation and geometry of carbon atoms in ethyne (HC≡CH), we need to count the number of sigma bonds and lone pairs around each carbon atom. This count helps us determine the steric number, which in turn dictates the hybridisation and molecular geometry.
C) sp hybridised with linear geometry. Each carbon atom in ethyne forms two sigma bonds and no lone pairs, leading to a steric number of 2, which corresponds to sp hybridisation and a linear geometry.
Why does carbon generally form covalent bonds rather than ions like C4+ or C4-?
Carbon atoms are too large to form ions
Removing or adding four electrons requires a very large amount of energy, making ion formation difficult
Carbon has no valence electrons available
Carbon does not obey the octet rule
The question asks why carbon primarily forms covalent bonds instead of ionic bonds, specifically avoiding \(\text{C}^{4+}\) or \(\text{C}^{4-}\) ions. This relates to the energy requirements for electron transfer and the stability of the resulting species.
Correct Option: B) Removing or adding four electrons requires a very large amount of energy, making ion formation difficult. This statement accurately explains why carbon prefers covalent bonding. Both the ionization energy to remove four electrons and the energy required to add four electrons are prohibitively high, making the formation of \(\text{C}^{4+}\) or \(\text{C}^{4-}\) ions energetically unfavorable.
The question asks for the systematic method of naming organic compounds based on internationally agreed rules. We need to identify the specific nomenclature system that provides a standardized way to name chemical compounds.
Correct Option: D) IUPAC nomenclature is the internationally recognized and systematic method for naming organic compounds, ensuring clarity and consistency in chemical communication.
The question asks to classify hydrocarbons like benzene, which have a closed ring of carbon atoms, delocalised electrons, and special stability. We need to identify the correct category among the given options based on these characteristics.
Correct Option: C) Aromatic hydrocarbons are characterized by a closed ring of carbon atoms, a delocalised system of pi electrons, and special stability (aromaticity), as exemplified by benzene.