Sagot :
Answer: Covalent bonds usually occur between nonmetals.
Explanation: For example, in water (H2O) each hydrogen (H) and oxygen (O) share a pair of electrons to make a molecule of two hydrogen atoms single bonded to a single oxygen atom. In general, ionic bonds occur between elements that are far apart on the periodic table.
Answer:
Carbon, silicon, germanium are all in the same group in the periodic table and they tend to make covalent bonds, especially carbon. All organic compounds contain carbon bound covalently to other atoms. There are carbides, which might be ionic. The name suggests that carbon is an anion in compounds such as tungsten carbide. However, I have not been able to confirm that. Boron is similar. There are borides but charged boron compounds contain an extra proton or extra hydride anion. In such cases, the charge is not found entirely on the boron, so I wouldn't say that compounds like borohydrides truly contain boron ionic bonds. In such cases, boron is covalently bonded to hydrogen.
Explanation:
A "covalent bond" is a bond between two atoms in which the electronegativity difference is not large enough so that the electrons appear to transfer completely to one atom (which is then considered an "ionic" bond).
The nonmetals (right side of the metalloids and hydrogen) are those that can form covalent bonds, because their outer shells are close enough to being full that they readily join with other nonmetals so that the shared electron pairs are sufficient to "fill" their valence shell.