Periodic table how does it work

Mendeleev arranged the elements according to both atomic weight and valence. Not only did he leave space for elements not yet discovered, but he predicted the properties of five of these elements and their compounds. In , he presented the findings to the Russian Chemical Society. Atomic number: The number of protons in an atom is referred to as the atomic number of that element. The number of protons defines what element it is and also determines the chemical behavior of the element.

For example, carbon atoms have six protons, hydrogen atoms have one, and oxygen atoms have eight. Atomic symbol : The atomic symbol or element symbol is an abbreviation chosen to represent an element "C" for carbon, "H" for hydrogen and "O" for oxygen, etc. These symbols are used internationally and are sometimes unexpected. For example, the symbol for tungsten is "W" because another name for that element is wolfram.

Also, the atomic symbol for gold if "Au" because the word for gold in Latin is aurum. Atomic weight : The standard atomic weight of an element is the average mass of the element in atomic mass units amu.

Individual atoms always have an integer number of atomic mass units; however, the atomic mass on the periodic table is stated as a decimal number because it is an average of the various isotopes of an element.

The average number of neutrons for an element can be found by subtracting the number of protons atomic number from the atomic mass. Atomic weight for elements For naturally occurring elements, the atomic weight is calculated from averaging the weights of the natural abundances of the isotopes of that element.

However, for lab-created trans-uranium elements — elements with atomic numbers higher than 92 — there is no "natural" abundance. Sometimes a periodic table cites a single value for atomic weight.

Other tables include two numbers, which represent a range of values. When a range is given, it's because the abundance of isotopes varies from one sampling location to another.

Mendeleev's original periodic table organized elements in order of increasing atomic mass or weight. The vertical columns are called groups. Each element in a group has the same number of valence electrons and typically behave in a similar manner when bonding with other elements.

The horizontal rows are called periods. Each period indicates the highest energy level the electrons of that element occupies at its ground state.

The bottom two rows—the lanthanides and actinides —all belong to the 3B group, and are listed separately. Many periodic tables include the element's name to help those who may not remember all the symbols for elements. Many periodic tables identify element types using different colors for different element types. These include the alkali metals , alkaline earths , basic metals , semimetals , and transition metals. The periodic table is organized to showcase the different trends periodicity.

The ability to accept an electron, electron affinity can be predicted based on element groups. Noble gases like argon and neon have an electron affinity near zero and tend not to accept electrons. Halogens like chlorine and iodine have high electron affinities.

Most other element groups have electron affinities lower than that of the halogens, but greater than the noble gases. Most of the elements are metals. Metals tend to be good electrical and thermal conductors, hard, and shiny. Nonmetals are clustered in the upper right hand section of the periodic table. The exception is hydrogen, which is on the top left of the table. A good periodic table is a great tool for solving chemistry problems. You can use an online periodic table or print your own.

Once you feel comfortable with the parts of the periodic table, quiz yourself to see how well you can read it. Actively scan device characteristics for identification. Each element within the periodic table has its own block. Within these blocks are identifying numbers and letters. The number on the very top is called the atomic number and it represents the number of protons in a single atom of the element. For the element helium shown above the atomic number is two. The letters in each block represent the atomic symbol.

This is essentially an abbreviation of the elements name. The atomic symbol for helium shown above is He. Lastly, the number in the bottom of each block is an elements atomic mass number. This number represents the average weight of a single atom of the element including protons and neutrons. In the case of helium, the atomic mass number is 4.

Notice that each vertical column of the periodic table above is marked by a set of identifiers 1A, 2A, 3B, 4B ect These are known as groups. The elements are arranged in these vertical groups because they share similar properties with each other. The elements are also arranged horizontally in rows called periods Shown above periods The elements in each period are not placed there at random.

Much like elements in a group, elements in a particular period all share similar properties. You may have noticed that the periodic table is also arranged in order of increasing atomic number. Hydrogen H is the first element with an atomic number of 1.