An alkane with 390 carbon atoms will have twice as many hydrogen atoms as carbon atoms. This is because each carbon atom forms four single bonds with other atoms, typically hydrogen atoms. Therefore, the alkane with 390 carbon atoms will have 780 hydrogen atoms. **

An alkane with 390 carbon atoms will have twice as many hydrogen atoms as carbon atoms. This is because each carbon atom forms four single covalent bonds, and each hydrogen atom forms one single covalent bond. Therefore, the number of hydrogen atoms in an alkane with 390 carbon atoms will be 780. **

Atoms can have isomers at 4 °C because isomers are molecules with the same molecular formula but different structural arrangements of atoms. At this temperature, atoms have enough thermal energy to allow for the rearrangement of bonds and formation of different isomeric structures. This thermal energy enables atoms to overcome activation energy barriers and transition between different isomeric forms. **

No, there is no known quadruple bond between two carbon atoms. Carbon typically forms strong covalent bonds with a bond order of 1, 2, or 3. While there are some examples of triple bonds between carbon atoms, quadruple bonds are not observed in carbon chemistry. The concept of quadruple bonding is more commonly associated with transition metal chemistry. **

OH groups are typically located on carbon atoms in organic compounds. Therefore, OH groups are located on C-atoms in compounds such as alcohols, carboxylic acids, and phenols. The number of C-atoms with OH groups can vary depending on the specific compound. **

The electronegativity difference between the carbon atoms in hexane is very small, as carbon has an electronegativity value of 2.55. This means that the carbon-carbon bonds are nonpolar. On the other hand, the electronegativity difference between the hydrogen atoms and the carbon atoms is also very small, as hydrogen has an electronegativity value of 2.20. Therefore, the carbon-hydrogen bonds in hexane are also nonpolar. Overall, the electronegativity differences in hexane are minimal, resulting in nonpolar covalent bonds throughout the molecule. **

Several name reactions can be used to link C-atoms, including the Wittig reaction, the Grignard reaction, the Suzuki coupling, the Heck reaction, and the Sonogashira coupling. These reactions involve the formation of carbon-carbon bonds through various mechanisms, such as nucleophilic addition, cross-coupling, or olefin metathesis. Each of these reactions offers unique advantages and can be used to selectively link C-atoms in different types of organic molecules. **

The time it takes to count 12g of carbon (C-atoms) would depend on the rate at which one can count individual atoms. Given that there are approximately 6.022 x 10^23 atoms in 12g of carbon (Avogadro's number), it would take an incredibly long time to count all of them individually. In fact, it would be practically impossible to count them all within a reasonable amount of time. Therefore, it is more practical to measure the mass of carbon using a scale or other analytical techniques rather than attempting to count individual atoms. **