The elements in the periodice table are not listed in alphabetical order, because the arragement in rows (periods) and columns (groups or familes), in increasing order of atomic number (number of protons of the atoms) permits to explain similarities among the elements, trend in some properties, and even predict properties of unknown elements.
For example, the elements of the first group (family), called alkaline metals, all have 1 valence electron, have similar physical properties (ductibility, malleability, luster, thermal and electricity conductivity), react in similar way with water, show a trend in the atomic radii and in the ionization energy.
You can tell similar stories for other groups like, alkalyne earth metals, halogens and noble gases.
You can also tell trends in electroneativities, and atomic radii, for a row of elements, as per the order they are in the row.
So, the current array resulted very helpul for chemists to explain and predict the behavior and properties of the elements.
<span>Double Displacement (Metathesis) hope this helps. </span>
<u>Answer:</u> The given amount of iron reacts with 9.0 moles of 
and produce 6.0 moles of 
<u>Explanation:</u>
We are given:
Moles of iron = 12.0 moles
The chemical equation for the rusting of iron follows:
By Stoichiometry of the reaction:
4 moles of iron reacts with 3 moles of oxygen gas
So, 12.0 moles of iron will react with = 
of oxygen gas
- <u>For iron (III) oxide:</u>
By Stoichiometry of the reaction:
4 moles of iron produces 2 moles of iron (III) oxide
So, 12.0 moles of iron will produce = 
of iron (III) oxide
Hence, the given amount of iron reacts with 9.0 moles of and produce 6.0 moles of
They become an ionic bond, and are weakly bonded compared to covalently bonded atoms
