Periodic Table Quiz

The rows of the periodic table are called periods, while the columns of the table are called groups. Elements in the same period share the same highest ground state electron energy level. Elements in the same group have the same number of valence electrons.

The Russian scientist Dmitri Mendeleev proposed a periodic table similar to the one we use today in 1869. He arranged the elements according to "periodic law", where element properties could be predicted based on recurring similarities between elements (periodicity).

The modern periodic table orders elements by increasing atomic number, which is the number of protons in the atom of the element. Mendeleev did not know about the parts of the atom, so he used the next best thing -- atomic weight.

Even though each atom has more electrons as you move from left to right across the periodic table, the atomic radius decreases. The reason is that you're also adding more protons, which exert a stronger attractive force on the electrons, drawing them in a tiny bit closer. Ionic radius also decreases, although not for the exact same reason.

As you move down a periodic table group, electronegativity decreases because the distance between the atomic nucleus and the valence electrons increases.

There are several ways to tell metals and nonmetals apart. Nonmetals don't have a metallic appearance. Unlike metals, they typically have lower melting and boiling points and tend not to conduct heat or electricity very well.

 About 75% of the elements on the periodic table are metals. The only groups that are not metals are the noble gases, halogens, and the group actually called nonmetals.

If you stop to think about it, the smallest atom is the one with the smallest number of protons. This is hydrogen, located in the top left side of the periodic table. Hydrogen is particularly small because the most common isotope doesn't have a neutron, plus it readily loses its electron.

In order for an atom to have a high electron affinity, it needs to be in a position to accept electrons. The alkaline earth metals (like calcium and magnesium) have filled s subshells, so they are stable. If anything, the alkaline earths prefer to lose electrons and exist as cations.

So, since elements like the alkaline earths that form cations have low electron affinity, it should make sense to you elements that form anions tend toward high electron affinity. Halogens (e.g., iodine, chlorine) have high electron affinity and also high electronegativity.