6.4: Modern Periodic Table- Periods and Groups (2024)

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    6.4: Modern Periodic Table- Periods and Groups (1)

    How has the English dictionary evolved over time?

    Language changes with time. New words enter the language and old words often disappear from lack of use. Dictionaries are published so that people can keep up with changes in language and know how to use words properly. These publications may be in print, as is thelawdictionary below, or they may be electronic. Dictionaries can be found on the internet and apps are available for smartphones. Dictionaries are invaluable for good, reliable communication.

    The Modern Periodic Table

    The periodic table has undergone extensive changes in the time since it was originally developed by Mendeleev and Moseley. Many new elements have been discovered, while others have been artificially synthesized. Each fits properly into a group of elements with similar properties. The periodic table is an arrangement of the elements in order of their atomic numbers, so that elements with similar properties appear in the same vertical column or group.

    The figure below shows the most commonly used form of the periodic table. Each square shows the chemical symbol of the element along with its name. Notice that several of the symbols seem to be unrelated to the name of the element: \(\ce{Fe}\) for iron, \(\ce{Pb}\) for lead, etc. Most of these are the elements that have been known since ancient times and have symbols based on their Latin names. The atomic number of each element is written above the symbol.

    6.4: Modern Periodic Table- Periods and Groups (2)

    A period is a horizontal row of the periodic table. There are seven periods in the periodic table, with each one beginning at the far left. A new period begins when a new principal energy level begins filling with electrons. Period 1 has only two elements (hydrogen and helium), while periods 2 and 3 have 8 elements. Periods 4 and 5 have 18 elements. Periods 6 and 7 have 32 elements, because the two bottom rows that are separatefrom the rest of the table belong to those periods. These two rowsare pulled out in order to make the table itself fit more easily onto a single page.

    A group is a vertical column of the periodic table, based on the organization of the outer shell electrons. There are a total of 18 groups. There are two different numbering systems that are commonly used to designate groups, and you should be familiar with both. The traditional system used in the United States involves the use of the letters A and B. The first two groups are 1A and 2A, while the last six groups are 3A through 8A. The middle groups use B in their titles. Unfortunately, there was a slightly different system in place in Europe. To eliminate confusion, the International Union of Pure and Applied Chemistry (IUPAC) decided that the official system for numbering groups would be a simple 1 through 18 from left to right. Many periodic tables show both systems simultaneously.

    Most recent depictions of the periodic table show an incomplete seventh period. In fact, many of those seventh period elements were not known before the early twentieth century. Many elements have been synthesized by bombarding known elements with sub-atomic particles such as neutrons oralphaparticles. Uranium has been used in this manner to produce elements 93-100. Larger elements (atomic numbers 101 and above) are formed by fusingnucleiof smaller elements together.

    These synthetic elements tend to be very unstable, often existing for less than a second, so little is known about them. Elements up to atomic number 112 are known (not in any detail, however), and some evidence for elements 113 and above had been put forth, with elements 114 and 116 being added to the table in 2011. In December 2015, the ​​​​​​​IUPAC verified the existence of four new elements 113, 115, 117, and 118 and approved their addition to the periodic table.

    The following are the new element names and their origins:

    • Element 113 was named Nihonium, symbol Nh, proposed by Japanese researchers after the Japanese word Nihon, which means Japan.
    • A team of scientists from Russia and the United States named element 115, Moscovium, symbol Mc, after Moscow and element 117, Tennessine, symbol Ts, after Tennessee.
    • The Russian team that discovered element 118 named it Oganesson, symbol Og, after Yuri Oganessian, a prolific element hunter.

    These elements complete the seventh period or row of the periodic table.

    The video below reviews groups and trends in the periodic table:

    Watch the additional videos below to learn more about the newly identified and named chemical elements:

    Element Name and Symbol: Nihonium (Nh)

    Atomic Number: 113

    Element Name and Symbol: Moscovium (Mc)

    Atomic Number: 115

    Element Name and Symbol: Tennessine (Ts)

    Atomic Number: 117

    Element Name and Symbol: Oganesson (Og)

    Atomic Number: 118


    • The periodic table is arranged in order of atomic number.
    • A period is a horizontal row of the periodic table.
    • A group is a vertical row of the periodic table.


    1. How is today’s periodic table different from the one that Mendeleev published?
    2. Are all the elements in today’s periodic table naturally occurring? Explain your answer.
    3. What is a “period"? What does it represent?
    4. What is a “group"? What does it represent?
    5. Why are there two different numbering systems for groups?
    6.4: Modern Periodic Table- Periods and Groups (2024)


    What are the groups and periods in the modern periodic table? ›

    The vertical columns in the periodic table are known as groups. The elements of the groups exhibit similar chemical and physical properties. The horizontal rows are called periods.

    Are there 8 or 18 groups? ›

    The s-, p-, and d-block elements of the periodic table are arranged into 18 numbered columns, or groups.

    What is period 4 Group 6 on the periodic table? ›

    Chromium. Chromium (Cr) is an element in group 6. Chromium is, like titanium and vanadium before it, extremely resistant to corrosion, and is indeed one of the main components of stainless steel.

    What element is Period 6 and Group 12? ›

    Expert-Verified Answer. The chemical element in period 6 and group 12 is mercury (Hg).

    How to find the period and group of an element? ›

    The number of shells is equal to its period number and the number of valence electrons tells us about its group. Let us take Oxygen for example. Its electronic configuration is 2, 6. It has two shells and 6 valence electrons.

    What are the 7 groups of the periodic table? ›

    Different groups are present in the periodic table:
    • The Alkali Metals.
    • The Alkaline Earth Metals.
    • The Transition Metals.
    • The Non-metals.
    • The Halogens.
    • The Noble Gases.
    • The Rare Earth Elements.

    What is group 6 on the periodic table? ›

    Group 6, numbered by IUPAC style, is a group of elements in the periodic table. Its members are chromium (Cr), molybdenum (Mo), tungsten (W), and seaborgium (Sg).

    What is group 8 called? ›

    These elements are known as noble gases. The valence electrons of the group are filled with filled eight electrons which makes these electrons non-reactive. They are stable and elements have a low energy state. They have elements Helium , Neon , Argon , Krypton , Xenon , and Radon .

    What are the 8 main groups of the periodic table? ›

    Name of the eight groups in the periodic table:
    • Alkali metals.
    • Alkaline earth metals.
    • Rare earth metals.
    • Crystallogens.
    • Pnictogens.
    • Chalcogens.
    • Halogens.
    • Noble gases.

    Where is period 6 on the periodic table? ›

    A period 6 element is an element in the sixth period (row) of the periodic table. It contains 32 elements, beginning at Caesium and ending with Radon. The Lanthanides (also called the rare earth elements) are part of this period. The lanthanides stretch from lanthanum (57) to lutetium (71).

    What are group 6 elements called? ›

    These elements are known as Chalcogens and are also known as the Oxygen family. Chalcogen is derived from the Greek word Chalco, which means"ore" and gen means “formation”.

    What is period 6 Group 13 on the periodic table? ›

    boron group element, any of the six chemical elements constituting Group 13 (IIIa) of the periodic table. The elements are boron (B), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), and nihonium (Nh).

    What is period 6 Group 17 on the periodic table? ›

    halogen, any of the six nonmetallic elements that constitute Group 17 (Group VIIa) of the periodic table. The halogen elements are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts).

    What is period 6 Group 14 on the periodic table? ›

    carbon group element, any of the six chemical elements that make up Group 14 (IVa) of the periodic table—namely, carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl).

    What is the group 16 period 6? ›

    oxygen group element, any of the six chemical elements making up Group 16 (VIa) of the periodic classification—namely, oxygen (O), sulfur (S), selenium (Se), tellurium (Te), polonium (Po), and livermorium (Lv).

    What are the 18 groups in the periodic table? ›

    Groups are numbered 1–18 from left to right. The elements in group 1 are known as the alkali metals; those in group 2 are the alkaline earth metals; those in 15 are the pnictogens; those in 16 are the chalcogens; those in 17 are the halogens; and those in 18 are the noble gases.

    What is a group in a periodic table? ›

    In the periodic table, there are 18 vertical columns, referred to as groups. A group contains elements with same number of electrons in their outermost shell due to which they show similar properties.

    How many groups and periods are there in mainly periodic table? ›

    There are 18 groups and 7 periods in the modern periodic table. Groups are vertical columns and periods are horizontal columns.

    What element is in period 4 group 12? ›

    Zinc group element | Properties, Uses & Compounds | Britannica.


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