- A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full valence shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonding is much more common than ionic bonding, where atoms are separate and merely associated by electrostatic attraction.
- Marfik (stars.astro.illinois.edu)
MARFIK (Lambda Ophiuchi). Double stars are among the prettiest sights the sky has to offer. The best ones, like Albireo and many others, display striking color contrasts that are enhanced by visual proximity effects. But even the white “colorless” ones are attractive, especially if the two members are close together. Those of Marfik (the “elbow” of Ophiuchus), or Lambda Ophiuchi, are so close that they are, however, difficult to separate at the telescope, averaging just a second of arc – a 3600th of a degree – apart.