You're likely asking about electronegativity, not "chloride numbers". Electronegativity is a measure of an atom's ability to attract electrons in a bond.

Here's how electronegativity relates to the periodic table:

* Increases across a period (left to right): As you move across a period, the number of protons in the nucleus increases, making the atom more attractive to electrons.

* Decreases down a group (top to bottom): As you move down a group, the electron shells increase in size, putting the valence electrons further from the nucleus and decreasing the attraction.

Therefore, the elements with the highest electronegativity are located in the upper right corner of the periodic table. Fluorine (F) is the most electronegative element.

Let me know if you have any other questions about the periodic table!