Why R-O-R is polar?

Answer 1

Element R takes a slightly positive charge, while O takes and negative charge.

The charge on O is twice R therefore you need two R's to balance R2O.

Because the R's are on either side of the O and the attraction is from to positive, the charges cancel each other out due to symmetry, one goes left 1 unit, the other goes right 1 unit, as they have an equal charge.

Answer 2

The R-O-R molecule is polar because the oxygen atom has a higher electronegativity than the carbon atoms, leading to an uneven distribution of electron density in the molecule. This causes a separation of charge, with the oxygen atom being partially negative and the carbon atoms being partially positive, resulting in a polar molecule.