Answer:
The *atomic* number
Explanation:
The atomic number is the number of protons in an atom of an element.
6 km/h west would be your answer
<span>The </span>elements are arranged<span> in order of increasing atomic number. Vertical columns(called groups) contain </span>elements with similar properties. Horizontal rows called periods elements with<span> the same number of atomic orbitals(That's why Hydrogen and Helium are separated from the rest of the table).
Hope this helps:)</span>
