Abond exists between a and b in the compound ab. a and b are sharing electrons. the type of bond is

Covalent

Explanation:

A covalent bond is formed when an element shares its valence electron with another element. This bond is formed between two non metals.  Example:

An ionic bond is formed when an element completely transfers its valence electron to another element. The element which donates the electron is known as electropositive element and the element which accepts the electrons is known as electronegative element. This bond is formed between a metal and an non-metal. Example:

Thus bond formed by sharing of electrons is covalent bond.

neutrons are in the middle of the atom and the electrons, which are much smaller.

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.