Who gave the first model of an atom? 

J.J. Thomson 

The correct answer is option 1. J.J. Thomson.

J.J. Thomson proposed the first model of an atom in 1904. His model is commonly known as the "plum pudding" model or the "raisin pudding" model.

In Thomson's model, the atom was considered to be a positively charged sphere with negatively charged electrons embedded within it, similar to raisins in a pudding or plums in a pudding. This model suggested that the atom was overall electrically neutral, with the positive and negative charges balanced.

Thomson's model was based on his discovery of the electron through his experiments with cathode rays. He observed that cathode rays (streams of electrons) were deflected by electric and magnetic fields, leading him to propose that electrons were negatively charged particles present within the atom.

While Thomson's plum pudding model contributed significantly to our understanding of atomic structure, it was later replaced by more sophisticated models, such as Ernest Rutherford's nuclear model and Niels Bohr's atomic model, which provided a more accurate description of the distribution of electrons within the atom. Nonetheless, Thomson's model represented an important step forward in the development of atomic theory.