Questions

The World Anti-Doping Agency (WADA) is a foundation created through a collective initiative led by the International Olympic Committee (IOC). It was set up on 10 November 1999 in Lausanne, Switzerland, as a result of what was called the "Declaration of Lausanne", to promote, coordinate and monitor the fight against drugs in sports. Since 2002, the organization's headquarters have been located in Montreal, Quebec, Canada.

The number of bonds between a pair of atoms is called the bond order.

Bond orders can be calculated from Lewis structures, which are the heart of the valence-bond model. Oxygen, for example, has a bond order of two.

When there is more than one Lewis structure for a molecule, the bond order is an average of these structures. The bond order in sulfur dioxide, for example, is 1.5  the average of an S-O single bond in one Lewis structure and an S=O double bond in the other.

In molecular orbital theory, we calculate bond orders by assuming that two electrons in a bonding molecular orbital contribute one net bond and that two electrons in an antibonding molecular orbital cancel the effect of one bond. We can calculate the bond order in the O₂ molecule by noting that there are eight valence electrons in bonding molecular orbitals and four valence electrons in antibonding molecular orbitals in the electron configuration of this molecule. Thus, the bond order is two.

The four bonds of carbon tetrachloride (CCl4) are polar, but the molecule is nonpolar because the bond polarity is cancelled by the symmetric tetrahedral shape. Hence, making the net dipole as zero and molecule as non-polar.

When other atoms substitute for some of the Cl atoms, the symmetry is broken and the molecule becomes polar.

Prokaryotic cells lack a nucleus and do not have an extensive system of interior membranes. They are encased in a cell wall and many contain external structures such as a capsule, flagellum, or pili. Prokaryotes – have a relatively uniform interior that is not subdivided by internal membranes.