14) Which of the following compounds is formed by covalent bonding? a) Na_(2)S b) AlCl_(3) c) CH_(4) d) LiCl

The correct answer is c) $CH_{4}$.<br /><br />Covalent bonding occurs when atoms share electrons to form a molecule. In the case of $CH_{4}$ (methane), the carbon atom shares electrons with four hydrogen atoms to form a covalent bond. This results in the formation of a stable molecule with a tetrahedral shape.<br /><br />On the other hand, the other options listed are formed by ionic bonding:<br /><br />a) $Na_{2}S$ (sodium sulfide) is formed by the transfer of electrons from sodium atoms to sulfur atoms, resulting in the formation of positively charged sodium ions and negatively charged sulfide ions.<br /><br />b) $AlCl_{3}$ (aluminum chloride) is formed by the transfer of electrons from aluminum atoms to chlorine atoms, resulting in the formation of positively charged aluminum ions and negatively charged chloride ions.<br /><br />d) LiCl (lithium chloride) is formed by the transfer of electrons from lithium atoms to chlorine atoms, resulting in the formation of positively charged lithium ions and negatively charged chloride ions.<br /><br />Therefore, the compound formed by covalent bonding is $CH_{4}$.