Question

I anm definitely not a halogen. But if all you knew about me
was my atomic mass (not my atomic number or properties).
then you might expect me to be located one element over in
the halogen family. Who am I?

Answer 1

The periodic law is a law relating the properties of the element with their

atomic numbers.

The element is potassium, K.

Reason:

By atomic mass, potassium is 39.10 g, while argon is 39.10 g.

Going by the atomic mass alone, potassium should come before argon in

the periodic table and therefore should be an halogen and not an alkali

metal.

However, the number of protons in the potassium is 19, and therefore larger

than the number of protons in argon, which is argon.

Therefore, the element is potassium, K.

Learn more about the periodic law here:

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