How can you represent atoms?

First you start of by finding out what the atomic number is of the element, in this case the number is 17.

You then draw a circle, you are aloud to put 2 electrons on this circle. you then draw another cirlce around it, you are aloud to have 8 electrons on the outer shells. you will ned a third circle to put the rest of the elcetrons on to it.

in total you should have the smallest circle with 2 electrons, the middle circle with 8 and then the outer shell with 7 elecrons on it. you can draw the electrons as dots or crosses on the cirlce line.

because the outer shell is not full and only has 7 electrons instead of 8, this means it will be reactive. if an element has a full outer shell then it becomes unreactive.

hope that helped. :)