_ _ _ _ _ _ is a good conductor of electricity. A. Iodine B. Graphite C. Sulphur D. Bromine
Hint: A good conductor of electricity is a substance that easily conducts electricity. Non-metals are bad conductors of electricity. However, there exists a non-metal made up of carbon atoms that is a good conductor of electricity.
Complete step by step answer: A good conductor of electricity is a substance that has a high value of electric conductance. Electric conductance of a substance is the ability of the substance to allow the electrons to flow through the conductor when a potential difference is created across the conductor. The elements of the periodic table are mostly metals and non-metals. Metals have a very high value of conductance because they contain free moving electrons. Hence, not much energy is required to move the electrons. In case of non-metals, the electrons are strongly bound to the nucleus, which makes it very difficult for the electrons to move when the potential difference is created. Therefore, they have a very low conductance. Hence, they are bad conductors of electricity. However, graphite is the only non-metal that easily conducts electricity. Graphite is made up of carbon atoms. The different carbon atoms are held together due to covalent bonds between their electrons. However, out of the four outermost electrons only three electrons participate in the bonding and layers of carbon atoms are formed. The non-bonded electrons reside in between these layers. Due to this, when a potential difference is produced across a graphite, it conducts electricity. Therefore, graphite is a good conductor of electricity.
Hence, the correct answer is option B.
Note: The other options- iodine, sulphur and bromine are non-metals. Hence, they are bad conductors of electricity. Not all the substances of carbon are good conductors of electricity. Diamond is also made up of carbon but it is a bad conductor of electricity. Graphite is a good conductor of electricity because it has free electrons.
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