Why are silver, platinum, palladium and osmium called noble metals?

What is the average rate of the reaction between 10 and 20 s?

When did stem cell research become known ? who discovered stem cell? what experiments or studies have been conducted so far?

What is the difference between covalent bonds and ionic bonds? covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the electrical attraction between charged atoms. covalent bonds involve the transfer of electrons between charged atoms; ionic bonds involve the sharing of electrons between atoms. covalent bonds involve the sharing of pairs of electrons between atoms; ionic bonds involve the sharing of single electrons between atoms. covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the sharing of protons between charged atoms.