What is the significance of groups and periods

For example, hydrogen and helium are in the same group and have one electron in the outer shell. Notice that the first period has only two elements. The second and the third periods have 8 elements each. Periods 4 and 5 each have 18 elements. Periods 6 and 7 are the exceptions as they contain 32 elements in total. This explains why the periodic table is shortened by removing part of period 6 and 7 and displaying right below the periodic table. The periodic would be large if the actinides and lanthanides were not removed.

These separated elements are inner transition metals and they fill the f-block in the atomic orbitals. The lanthanides include the elements from 58 through to 71 while the actinides include the elements from 89 through to The other characteristic that the elements within a period shares is an increase in ionization energy. Atoms within a period increase in atomic numbers as more protons are increasingly added. This increases the attraction in the nucleus and it will become relatively hard to remove an electron.

The nuclear charge increase across the periodic table. Also, electronegativity increases as you move from left to right across the period. Electron affinity also increases as more electrons are added thus increasing a strong force of attraction with the nucleus.

As you count down from top to bottom along the columns, you are counting the groups. The US style uses As and Bs. Each of the 18 groups bears a name. For instance, the first group is known as the lithium family alkali metals , group 2 the beryllium family alkaline earth metals, group 3 the scandium family, group 4 the titanium family, group 5 the vanadium family, group 6 the chromium family, group 7 the manganese family, group 8 the iron family, group 9 the cobalt family, group 10 the nickel family, group 11 the copper family coinage metals , group 12 the zinc family volatile metals , group 13 the boron family icoasagens , group 14 carbon family crystallogens, tetrels , group 15 the nitrogen family pentels , group 16 the oxygen family chalcogens , group 17 the fluorine family halogens , and group 18 the helium or neon family noble gases.

The elements within a group share chemical or physical properties. Group 18, for example, is referred to as noble gases. They are non-reactive with any other elements. The octet rule of 8 electrons in the outer shell applies perfectly to the noble gases.

All other elements strive to achieve the octet rule. Hydrogen does not follow the octet rule and so is helium although it is stable and part of the noble gases. Period table has a mix of metals, non-metals and metalloids semimetals. The elements in this group are also gases at room temperature. In this numbering system, group 1A is group 1; group 2A is group 2; the halogens 7A are group 17; and the noble gases 8A are group You will come across periodic tables with both numbering systems.

It is important to recognize which numbering system is being used and to be able to find the number of valence electrons in the main block elements regardless of which numbering system is being used. If you can locate an element on the Periodic Table, you can use the element's position to figure out the energy level of the element's valence electrons.

A period is a horizontal row of elements on the periodic table. Skills to Develop Give the name and location of specific groups on the periodic table, including alkali metals, alkaline earth metals, noble gases, halogens, and transition metals. Explain the relationship between the chemical behavior of families in the periodic table and their electron configurations. Identify elements that will have the most similar properties to a given element.

Families of the Periodic Table Remember that Mendeleev arranged the periodic table so that elements with the most similar properties were placed in the same group. Periods of the Periodic Table If you can locate an element on the Periodic Table, you can use the element's position to figure out the energy level of the element's valence electrons. Summary The vertical columns on the periodic table are called groups or families because of their similar chemical behavior.

All the members of a family of elements have the same number of valence electrons and similar chemical properties. Groups and periods organize elements on the periodic table of the elements. A group is a vertical column down the periodic table, while a period is a horizontal row across the table. Both groups and periods reflect the organization of electrons in atoms.

Element atomic number increases as you move down a group from top to bottom or across a period from left to right. Elements within the same group share the same number of valence electrons. The number of valence electrons depends on the octet rule. For example, elements in group 1 have 1 valence electron, elements in groups have a variable number of valence electrons, and elements in group 17 have 7 valence electrons.

The lanthanides and actinides, located below the main table, all fit within group 3.