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Families of the Periodic Table
Mendeleev managed to arranged the periodic table so that elements with the most similar properties were placed in the same group. Elements are placed into families due to their similar properties, characteristics, and reactivities.Elements in the same group have similar physical and chemical properties.. A group, or family of elements, is a vertical column of the periodic table. The periodic table has seven periods and 18 groups.
Group 1 Elements
Group 1 elements are also called alkali metals. They include: lithium, sodium, potassium, rubidium, cesium, and francium. All of the elements in group 1 (except for hydrogen, which has unique properties) are very reactive and form compounds in the same ratios and with similar properties as other 1 element. Due to the similarities in their chemical properties, Mendeleev put these elements into the same group and they came to be known as the alkali metals.. Alkali metals are among the most reactive metals. This is due in part to their larger atomic radii and low ionization energies. Alkali metals have a soft texture, are silvery in color and can be easily cut. They also have low boiling and melting points and are less dense than most elements.
Group 2 Elements ( Alkaline earth metals)
Once again these elements have similar properties to each other. Alkaline earth metals include Beryllium, Magnesium, Calcium, Barium, Strontium and Radium and are soft, silver metals that are less metallic in character than the Group 1 alkali metals. Although many characteristics are common throughout the group, the heavier metals such as Ca, Sr, Ba, and Ra are almost as reactive as the Group 1 alkali metals. They get their name because early “scientists” found that all of the alkaline earth metals were found in the earth’s crust.
The Transition Metals
The transition metals are the larger block of elements extending from Groups 3-12 (also known as the group B elements). Transition elements differ from the main group elements (group A elements) in that they tend to be hard and have high densities. They have high melting points and boiling points and can show various oxidation states when forming chemical bonds (this will be discussed further in chapter 3). Transition metals have high melting points and boiling points, often form colored compounds that are highly stable, and they can serve as good catalysts. A catalyst is an agent that helps to speed up a chemical reaction without itself being changed in the process.
Halogens ( Group 17 elements)
This group contains very reactive nonmetals. The halogens are an interesting group. Halogens are members of Group 7, which is also referred to as 7A. It is the only group in the Periodic Table that contains all of the states of matter at room temperature. Fluorine, F2 and chlorine, Cl2 are gases, while Bromine, Br2, is a liquid and iodine, I2, and astatine, At2, are both solids. Another interesting feature about Group 17 is that it houses four (4) of the seven (7) diatomic elements. Diatomic elements only exist in nature as a pair of atoms of the same element that are bonded together. The seven diatomic elements are H2, N2, O2, F2, Cl2, Br2, and I2. Notice that the latter four are Group 17 elements. The word halogen comes from the Greek meaning salt forming. French chemists discovered that the majority of halogen ions will form salts when combined with metals.
The Noble Gases
The noble gases are in group 18. The two most significant properties of noble gases is that they are extremely unreactive, rarely forming compounds, and that they all exist as gases at room temperature. The noble gases were actually considered inert gases until the 1960s when a compound was formed between xenon and fluorine which changed the way chemists viewed the “inert” gases. In the English language, inert means to be lifeless or motionless; in the chemical world, inert means does not react. Later, the name “noble gas” replaced “inert gas” for the name of Group 18. The elements in this group are also gases at room temperature.