Chemists like to put things together into groups based on similar properties. This process, called classfication, makes studying a particular system much easier. Scientists grouped the elements in the periodic table so they donot have to memorize the properties of individual elements. With the periodic table, they can just remember the properties of the various groups.
The periodic table is the most important tool a chemist possesses. So in this post, I tell you how the elements are arranged in the table, and I show you some important groups. I also explain how chemists and other scientists use the periodic table.
Repeating Patterns: The Modern Periodic Table
In nature, as well as in things that humankind invents, You may notice some repeating patterns. The seasons repeat their pattern of fall, winter, spring, and summer. The tides repeat their pattern of rising and falling. Tuesday follows Monday, December follows November, and so on. A pattern of repeating order is called periodicity.
In the mid-1800s, Dmitri Mendeleev, a Russian chemist, noticed a repeating pattern of chemical properties in the elements that were known at the time. Mendeleev arranged the elements in order of increasing atomic mass to form something that fairly closely resembles the modern Periodic Table. He was even able to predict the properties of some of the then-unknown elements. Later, the elements were rearranged in order of increasing atomic number, the number of protons in the nucleus of the atom.
PERIODIC TABLE FIGURE-
The periodic table is the most important tool a chemist possesses. So in this post, I tell you how the elements are arranged in the table, and I show you some important groups. I also explain how chemists and other scientists use the periodic table.
Repeating Patterns: The Modern Periodic Table
In nature, as well as in things that humankind invents, You may notice some repeating patterns. The seasons repeat their pattern of fall, winter, spring, and summer. The tides repeat their pattern of rising and falling. Tuesday follows Monday, December follows November, and so on. A pattern of repeating order is called periodicity.
In the mid-1800s, Dmitri Mendeleev, a Russian chemist, noticed a repeating pattern of chemical properties in the elements that were known at the time. Mendeleev arranged the elements in order of increasing atomic mass to form something that fairly closely resembles the modern Periodic Table. He was even able to predict the properties of some of the then-unknown elements. Later, the elements were rearranged in order of increasing atomic number, the number of protons in the nucleus of the atom.
PERIODIC TABLE FIGURE-
Arranging Elements in the Periodic Table
Look at the periodic table figure. Here the elements are arranged in order of increasing atomic number. The atomic number (number of protons) is located right above the element symbol. Under the element symbol is the atomic mass, or atomic weight. Atomic mass is a weighted average of all naturally occurring isotopes.
Notice that two rows of elements - Ce -Lu (commonly called the lanthanides) and Th-Lr (the actinides) - have been pulled out of the main body of the periodic table, the table would be much wider.
Using the periodic table, you can classify the elements in many ways. Two quite useful ways are -
1. Metals, Nonmetals, and Metalloids
2. Families and periods
Grouping metals, Nonmetals, and Metalloids
Elements can be metals, nonmetals, or metalloids. In this section, I explain their properties.
Metals
If you look at the periodic table figure, you can see a stair-stepped line starting at boron (B), atomic number 5, and going all the way down to polonium (Po), atomic number 84. Except for germanium (Ge) and antimony (Sb), all the elements to the left of that line can be classified as metals. Figure 2 given below which shows metals.
These metals have Properties that you normally associate with the metals you encounter in everyday life. They're solid at room temperature (with the exception of mercury, Hg, a liquid), shiny, good conductors of electricity and heat, ductile (they can be drawn into thin wires), and malleable (they can be easily hammered into very thin sheets). All these metals tend to lose electrons easily. As you can see, the vast majority of the elements on the periodic table are classified as metals.
Nonmetals
Except for the elements that border the stair-stepped line (more on those in a second), the elements to the right of the line, along with hydrogen, are classified as nonmetals.
See the figure below-
Nonmetals have properties opposite those of the metals. The nonmetals are brittle, aren't malleable or ductile, and are poor conductors of both heat and electricity. They tend to gain electrons in chemical reactions. Some nonmetals are liquids at room temperature.
Metalloids
The elements that border the stair-stepped in the periodic table are classified as metalloids, and see the figure given below. The metalloids, or semimetals, have properties that are somewhat of a cross between metals and nonmetals. They tend to be economically important because of their unique conductivity properties (they only partially conduct electricity). which make them valuable in the semiconductor and computer chip industry. (The term Silicon Valley doesnot refer to a valley covered in sand; silicon, one of the metalloids, is used in making computer chips.)
Arranging Elements By Families and Periods
Note: The periodic table is composed of horizontal rows and vertical columns. Here's how they're named and numbered.
Periods
The seven horizontal rows are called periods. The periods are numbered 1 through 7 on the left-hand side of the periodic table figure given above. Within each period, the atomic numbers increase from left to right.
Members of a period donot have very similar properties. Consider the first two members of period 3: sodium (Na) and magnesium (Mg). In reactions, they both tend to lose one electron, and magnesium loses two. Chlorine (Cl), down near the end of the period, tends to gain an electron (it's a nonmetal)
Families
The vertical columns are called groups, or families. The families may be labeled at the top of the columns in one of two ways. The older method uses roman numerals and letters. Many chemists (especially academic ones) prefer and still use this method, so that's what I use in describing the features of the table. The newer method simply uses the numbers 1 to 18.
The members of a family do have similar properties. Consider the IA family, starting with lithium (Li) and going through francium (Fr) (donot worry about hydrogen, because it's unique, and it doesn't really fit anywhere). All these elements tend to lose only one electron in reactions.
And all the members of the VIIA family tend to gain one electron.
If you have still any doubts, Then feel free to comment us.