Answer:
Dalton's atomic theory was the first complete attempt to describe all matter in terms of atoms and their properties.
Dalton based his theory on the law of conservation of mass and the law of constant composition.
The first part of his theory states that all matter is made of atoms, which are indivisible.
The second part of the theory says all atoms of a given element are identical in mass and properties.
The third part says compounds are combinations of two or more different types of atoms.
The fourth part of the theory states that a chemical reaction is a rearrangement of atoms.
Parts of the theory had to be modified based on the existence of subatomic particles and isotopes
The fact that most alpha particles went straight through the foil is evidence for the atom being mostly empty space. A small number of alpha particles being deflected at large angles suggested that there is a concentration of positive charge in the atom.
Dipole moment can be defined as the product of magnitude of charge and the distance of separation between the charges. A dipole exists when two or more atoms with different electronegativities are bonded together to form a molecule. The resulting unequal sharing of electrons leads to a molecule with a net positive and a net negative end. Hence the molecule is said polar.
Bonds between carbon and oxygen (C=O) are more polar but carbon dioxide (CO2) does not exhibits a dipole moment because CO2 is a linear molecule and the charge is equally distributed amongst the entire molecule. When molecules have an even charge distribution then there is no dipole moment and the molecule is said to be non-polar. CO2 is a linear molecule, so the dipoles are symmetrical and are equal in magnitude but point in opposite directions so they cancel out each other effect and we get net dipole moment zero.
On the other hand sulfur dioxide (SO2) exhibits a dipole moment because unlike CO2 molecule SO2 is not a linear molecule because of the presence of lone pair on Sulfur (S) atom , the geometry of SO2 is bent. This bent orientation of the oxygen's with respect to the sulfur results in the uneven distribution of positive and negative charges between the sulfur atom and the two oxygen atoms in the diagonal-shaped sulfur dioxide molecule. So the dipoles are not equal in magnitude and they do not cancel out and SO2 molecule exhibit a net dipole moment.
NOTE: If the molecule is linear, the dipoles are equal and exactly opposite in direction, so like a perfectly equal tug-of-war, they cancel each other out, and there is no net dipole in the molecule.
CO2 (linear molecule) = The dipoles are equal and exactly opposite in direction. They cancel each other out, and there is no net dipole in the molecule.
SO2 ( bent shape not linear) = Their is an uneven distribution of positive and negative charges between the sulfur atom and the two oxygen atoms. Dipoles are not equal in magnitude and they do not cancel out and SO2 molecule exhibit a net dipole moment.