The answer is Kepler's first law. Kepler's first law<span> - sometimes referred to as the </span>law of harmonies<span> - compares the orbital period and radius of orbit of a planet to those of other planets. Unlike Kepler's first and second laws that describe the motion characteristics of a single planet, the third law makes a comparison between the motion characteristics of different planets. The comparison being made is that the ratio of the squares of the periods to the cubes of their average distances from the sun is the same for every one of the planets. Hope that helped</span>
Elements are made of only one kind of atom. The molecule is made up of two or more kinds of atoms. There is no physical change that can separate the compounds into more than one kind of substance. This makes a compound a pure substance.
The elements of group 18 of periodic table are called as noble gases. They are stable because they have complete valence shell electrons. So there octet rule is satisfied.
When the transfer of electrons occurs, an electrostatic attraction between the two ions of opposite charge takes place and an ionic bond is formed. A salt such as sodium chloride (NaCl) is a good example of a molecule with ionic bonding
