The Periodic Table
Part of the Inorganic Chemistry For Dummies Cheat Sheet
The table is like a shelf that is used to organize all the elements found in nature, and some that are man-made even. It is useful because it arranges each element into a box, sort of like how you arrange your kitchen into hot spices, sweet spices, sugar, and flour, for example. So when you want to cook up a storm, you know where to get the ingredients necessary; you can think of the periodic table as nature’s list of ingredients. Learning the properties of each ingredient and knowing what happens when they are mixed at certain concentrations at specific temperatures and pressure is what an inorganic chemist does.
The periodic table can be used to determine the following properties of materials:
Atomic number (Z): Elements are all organized according to their atomic number and arranged in order from low atomic numbers to high atomic numbers. The atomic number itself can also tell you lots about the element; it can help to understand the valency, the coordination number, and the position you would expect to find it on the periodic table. Atomic numbers range from 1 to 118. The atomic number represents the number of protons that exist in the nucleus.
Number of protons: The proton makes up a part of the nucleus. It’s a positively charged particle that is counterbalanced by electrons, but the electrons orbit around the outside instead. The number of protons can determine how many electrons can orbit around the atom; this, in turn, affects the reactivity and chemistry of the atom.
Reactivity: The reactivity of the elements increases going from left to right on the periodic table. Each element going from left to right tends to be more reactive. But, at the far right are the noble gasses, and they are almost completely inert. The reactivity all increases as you go down the periodic table, for example rubidium is far more reactive than sodium.
Electronegativity: This property determines how much the element attracts electrons. This is also a good measure of reactivity, because the more that an element attracts electrons, the more reactive it is. The most electronegative element on the table is fluorine. The electronegativity increases going from left to right, and it decreases going down the table.
Mass: As you go from left to right and from top to bottom, you are always adding more protons in the atom. This has the general trend to make the later elements heavier than the earlier elements. But you should realize that this is only a general trend, and there are some exceptions to the rule.
Density: As you go down the table, the density of the atom increases; as you go from left to right the density also increases.
Moving left to right across the periodic table shown in the following figure, the atomic size decreases because of the additional nuclear charge due to addition of neutrons and protons in the nucleus. This makes the orbital electrons be more tightly bound, and the ionization energy increases because of that.