All the different elements are arranged in the periodic table. Here are the main features of the table:. Since the families of elements were organized by their chemical behavior, it is predictable that the individual members of each chemical family will have similar electron configurations. Remember that Mendeleev arranged the periodic table so that elements with the most similar properties were placed in the same group. A group is a vertical column of the periodic table.
All of the 1A elements have one valence electron. This is what causes these elements to react in the same ways as the other members of the family. The elements in 1A are all very reactive and form compounds in the same ratios with similar properties with other elements. Because of their similarities in their chemical properties, Mendeleev put these elements into the same group. Group 1A is also known as the alkali metals. Although most metals tend to be very hard, these metals are actually soft and can be easily cut.
Group 2A is also called the alkaline earth metals. Transition metals: Returning to the main body of the table, the remainder of Groups 3 through 12 represent the rest of the transition metals. Hard but malleable, shiny, and possessing good conductivity, these elements are what you typically think of when you hear the word metal. Many of the greatest hits of the metal world — including gold, silver, iron and platinum — live here.
Post-transition metals: Ahead of the jump into the nonmetal world, shared characteristics aren't neatly divided along vertical group lines. These elements have some of the classic characteristics of the transition metals, but they tend to be softer and conduct more poorly than other transition metals. Many periodic tables will feature a bolded "staircase" line below the diagonal connecting boron with astatine. The post-transition metals cluster to the lower left of this line.
They form the staircase that represents the gradual transition from metals to nonmetals. These elements sometimes behave as semiconductors B, Si, Ge rather than as conductors. Metalloids are also called "semimetals" or "poor metals. Nonmetals: Everything else to the upper right of the staircase — plus hydrogen H , stranded way back in Group 1 — is a nonmetal. Halogens: The top four elements of Group 17, from fluorine F through astatine At , represent one of two subsets of the nonmetals.
The halogens are quite chemically reactive and tend to pair up with alkali metals to produce various types of salt. So it would be argon, then 3d1 4s2. And to get things in the right order for our shells, let me put the 3d1 before the 4s2.
And so when people think about the aufbau principle, they imagine all of these d-block elements as somehow filling the d-block. Now as we know in other videos, that's not exactly true, but when you're conceptualizing the electron configuration it might be useful. Then you come over here and you start filling the p-block. So for example, if you look at the electron configuration for, let's say carbon, carbon is going to have the same electron configuration as helium, as helium, and then you're going to fill your s-block 2s2, and then 2p one 2.
So 2p2. So how many valence electrons does it have? Well, in its second shell, its outermost shell, it has two plus two, it has four valence electrons, and that's going to be true for the things in this group, and because of that, carbon has similar bonding behavior to silicon, to the other things in its group.
And we can keep going on, you know, for example, oxygen, oxygen and sulfur, these would both want to take two electrons from someone else because they have six valence electrons, they want to get to eight, so they have similar bonding behavior. You go to this yellow group right over here, these are the halogens. So there's a special name for them. These are the halogens. And these are highly reactive, because they have seven valence electrons. They would love nothing more than to get one more valence electron, so they love to react, in fact, they especially love to react with the alkali metals over here.
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