why is the periodic table arranged by increasing atomic number instead of increasing atomic mass?

Answer 1

Because doing it that way puts elements with similar chemical characteristics together in the vertical columns.

Atomic number is also the number of electrons. The electrons decide the chemistry.

Answer 2

Because the Atomic Number refers to specific elements whereas atomic mass does not. A good example is that of carbon. Its Atomic Number is six since it always contains six protons. If it had five protrons it wouldn't be carbon, it would be boron. If it had seven protrons it wouldn't be carbon, it would be nitrogen. The Atomic Weight is the number of protons along with the relative abundance of the numbers of neutrons in the nucleus. Since most carbon has six neutrons the atomic mass is slightly over 12 (12.011 if I remember correctly). The extra mass is due to that small percentage (less than 1%, I believe) of carbon that has 7 neutrons (Carbon 13) or 8 neutrons (the radioactive Carbon 14) Also, the number of electrons in an atom can change and this leads to ions. Carbon has a valence of +2,+4 and -4, in addition to the ground state of 0. That means that carbon can have 4, 6, 8 or 10 electrons. Since more or less electrons can change carbon into an ions and more neutrons can change the isotopes of carbon it is best to stick to a sub-atomic particle that cannot change without changing the type of element that it is.

Answer 3

It's a lot easier, since we can just count 1, 2, 3...
But also, it's arranged by the amount of protons each element has. If you look at it, it actually IS arranged by increasing atomic mass, just not nice, round numbers :)

Answer 4

An atom's atomic number refers to the number of protons or electrons present.

It is believed that the arrangement of atoms in the periodic table was due to the number of electrons that each atom possesses.

Answer 5

Periodic Table Ni

Answer 6

because vertical groups contain similar characteristics within the elements, for instance if you look on a periodic table at argon, it is slightly heavier than potassium, the next element on the table. If it were arranged by atomic mass, argon and potassium would be switched, an obvious error seeing as how potassium is an alkali metal and highly reactive and argon is a noble gas, very unreactive.

Answer 7

It wouldn't be periodic if organized by atomic mass. it is the atomic number that determines the principal properties of the elements.