Which Families on the Periodic Table Are the Most Reactive?

2.5 The Periodic Table

Learning Objectives

Past the end of this section, y'all volition be able to:

• State the periodic police and explain the organisation of elements in the periodic tabular array
• Predict the general properties of elements based on their location within the periodic table
• Identify metals, nonmetals, and metalloids by their properties and/or location on the periodic tabular array

As early chemists worked to purify ores and discovered more elements, they realized that various elements could be grouped together by their similar chemical behaviors. One such group includes lithium (Li), sodium (Na), and potassium (K): These elements all are shiny, conduct heat and electricity well, and accept similar chemic properties. A second group includes calcium (Ca), strontium (Sr), and barium (Ba), which also are shiny, good conductors of heat and electricity, and have chemical properties in common. All the same, the specific properties of these two groupings are notably different from each other. For example: Li, Na, and K are much more reactive than are Ca, Sr, and Ba; Li, Na, and M form compounds with oxygen in a ratio of two of their atoms to one oxygen cantlet, whereas Ca, Sr, and Ba form compounds with one of their atoms to one oxygen atom. Fluorine (F), chlorine (Cl), bromine (Br), and iodine (I) likewise exhibit similar backdrop to each other, but these properties are drastically unlike from those of any of the elements higher up.

Dimitri Mendeleev in Russian federation (1869) and Lothar Meyer in Frg (1870) independently recognized that at that place was a periodic relationship amongst the backdrop of the elements known at that time. Both published tables with the elements arranged co-ordinate to increasing atomic mass. But Mendeleev went one step further than Meyer: He used his table to predict the existence of elements that would have the properties like to aluminum and silicon, but were still unknown. The discoveries of gallium (1875) and germanium (1886) provided groovy support for Mendeleev's piece of work. Although Mendeleev and Meyer had a long dispute over priority, Mendeleev's contributions to the development of the periodic tabular array are now more widely recognized (Figure 1).

Figure 1. (a) Dimitri Mendeleev is widely credited with creating (b) the beginning periodic table of the elements. (credit a: modification of piece of work by Serge Lachinov; credit b: modification of work past "Den fjättrade ankan"/Wikimedia Commons)

By the twentieth century, it became apparent that the periodic relationship involved atomic numbers rather than atomic masses. The modern argument of this relationship, the periodic police force, is as follows: the properties of the elements are periodic functions of their atomic numbers. A modern periodic table arranges the elements in increasing order of their atomic numbers and groups atoms with like backdrop in the same vertical column (Effigy 2). Each box represents an element and contains its atomic number, symbol, average atomic mass, and (sometimes) name. The elements are arranged in vii horizontal rows, called periods or series, and 18 vertical columns, chosen groups. Groups are labeled at the top of each column. In the United States, the labels traditionally were numerals with capital messages. However, IUPAC recommends that the numbers 1 through eighteen be used, and these labels are more common. For the tabular array to fit on a single page, parts of two of the rows, a full of 14 columns, are normally written below the main trunk of the table.

Figure 2. Elements in the periodic tabular array are organized according to their properties.

Many elements differ dramatically in their chemical and concrete properties, just some elements are similar in their behaviors. For example, many elements announced shiny, are malleable (able to be deformed without breaking) and ductile (tin can be fatigued into wires), and comport heat and electricity well. Other elements are not shiny, malleable, or ductile, and are poor conductors of heat and electricity. We can sort the elements into large classes with mutual properties: metals (elements that are shiny, malleable, good conductors of rut and electricity—shaded xanthous); nonmetals (elements that announced tedious, poor conductors of heat and electricity—shaded green); and metalloids (elements that conduct rut and electricity moderately well, and possess some backdrop of metals and some properties of nonmetals—shaded royal).

The elements can likewise be classified into the principal-group elements (or representative elements) in the columns labeled 1, 2, and 13–18; the transition metals in the columns labeled three–12; and inner transition metals in the ii rows at the bottom of the table (the top-row elements are called lanthanides and the bottom-row elements are actinides; Effigy three). The elements can be subdivided further by more than specific properties, such as the composition of the compounds they form. For example, the elements in group ane (the offset column) course compounds that consist of 1 cantlet of the chemical element and one atom of hydrogen. These elements (except hydrogen) are known every bit brine metals, and they all have similar chemical properties. The elements in group 2 (the second cavalcade) form compounds consisting of one atom of the element and ii atoms of hydrogen: These are called alkaline world metals, with like properties among members of that group. Other groups with specific names are the pnictogens (group 15), chalcogens (group 16), halogens (group 17), and the noble gases (group 18, also known as inert gases). The groups can likewise be referred to past the get-go chemical element of the group: For case, the chalcogens can be chosen the oxygen group or oxygen family. Hydrogen is a unique, nonmetallic element with backdrop similar to both grouping 1A and grouping 7A elements. For that reason, hydrogen may be shown at the height of both groups, or by itself.

Effigy 3. The periodic tabular array organizes elements with similar properties into groups.

Click on this link for an interactive periodic table, which you can use to explore the backdrop of the elements (includes podcasts and videos of each element). You lot may also desire to effort this one that shows photos of all the elements.

Example 1

Naming Groups of Elements
Atoms of each of the following elements are essential for life. Give the group name for the following elements:

(a) chlorine

(b) calcium

(c) sodium

(d) sulfur

Solution
The family unit names are as follows:

(a) halogen

(b) alkaline earth metal

(c) brine metallic

(d) chalcogen

Bank check Your Learning
Requite the group name for each of the following elements:

(a) krypton

(b) selenium

(c) barium

(d) lithium

Answer:

(a) noble gas; (b) chalcogen; (c) alkaline earth metallic; (d) alkaline

In studying the periodic table, you might accept noticed something about the diminutive masses of some of the elements. Element 43 (technetium), chemical element 61 (promethium), and about of the elements with atomic number 84 (polonium) and higher take their atomic mass given in foursquare brackets. This is done for elements that consist entirely of unstable, radioactive isotopes (you lot volition acquire more most radioactivity in the nuclear chemistry chapter). An average atomic weight cannot be determined for these elements considering their radioisotopes may vary significantly in relative abundance, depending on the source, or may non fifty-fifty exist in nature. The number in foursquare brackets is the atomic mass number (and approximate atomic mass) of the most stable isotope of that element.

Key Concepts and Summary

The discovery of the periodic recurrence of like properties among the elements led to the formulation of the periodic table, in which the elements are arranged in order of increasing diminutive number in rows known as periods and columns known every bit groups. Elements in the same grouping of the periodic tabular array take like chemical backdrop. Elements can exist classified as metals, metalloids, and nonmetals, or as a main-group elements, transition metals, and inner transition metals. Groups are numbered 1–eighteen from left to right. The elements in group 1 are known equally the alkali metals; those in group 2 are the alkaline metal 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.

Chemistry Stop of Affiliate Exercises

1. Using the periodic table, allocate each of the following elements as a metal or a nonmetal, and then further allocate each every bit a main-group (representative) element, transition metal, or inner transition metal:

   (a) uranium

   (b) bromine

   (c) strontium

   (d) neon

   (due east) gold

   (f) americium

   (grand) rhodium

   (h) sulfur

   (i) carbon

   (j) potassium

2. Using the periodic table, classify each of the following elements as a metal or a nonmetal, and then further classify each equally a main-group (representative) element, transition element, or inner transition metal:

   (a) cobalt

   (b) europium

   (c) iodine

   (d) indium

   (e) lithium

   (f) oxygen

   (h) cadmium

   (i) terbium

   (j) rhenium

3. Using the periodic tabular array, identify the lightest member of each of the following groups:

   (a) noble gases

   (b) alkaline earth metals

   (c) alkali metals

   (d) chalcogens

4. Using the periodic table, place the heaviest member of each of the post-obit groups:

   (a) alkali metals

   (b) chalcogens

   (c) noble gases

   (d) alkaline world metals

5. Use the periodic tabular array to give the name and symbol for each of the following elements:

   (a) the element of group 0 in the same period as germanium

   (b) the element of group i earth metal in the same catamenia as selenium

   (c) the halogen in the same flow as lithium

   (d) the chalcogen in the same period equally cadmium

6. Use the periodic table to requite the proper noun and symbol for each of the following elements:>

   (a) the halogen in the same period every bit the alkali metallic with 11 protons

   (b) the alkaline earth metal in the same period with the neutral element of group 0 with 18 electrons

   (c) the noble gas in the aforementioned row as an isotope with xxx neutrons and 25 protons

   (d) the noble gas in the same period as gilt

7. Write a symbol for each of the post-obit neutral isotopes. Include the atomic number and mass number for each.

   (a) the element of group i with eleven protons and a mass number of 23

   (b) the noble gas element with 75 neutrons in its nucleus and 54 electrons in the neutral atom

   (c) the isotope with 33 protons and 40 neutrons in its nucleus

   (d) the alkaline earth metal with 88 electrons and 138 neutrons

8. Write a symbol for each of the post-obit neutral isotopes. Include the diminutive number and mass number for each.

   (a) the chalcogen with a mass number of 125

   (b) the halogen whose longest-lived isotope is radioactive

   (c) the noble gas, used in lighting, with 10 electrons and 10 neutrons

   (d) the lightest brine metallic with three neutrons

Glossary

actinide

inner transition element in the bottom of the bottom two rows of the periodic table

alkali metal

element in group 1

alkaline earth metal

element in group 2

chalcogen

element in group 16

group

vertical column of the periodic table

halogen

element in grouping 17

inert gas

(besides, noble gas) element in grouping 18

inner transition metal

(too, lanthanide or actinide) element in the bottom two rows; if in the showtime row, also chosen lanthanide, or if in the second row, as well called actinide

lanthanide

inner transition element in the top of the bottom two rows of the periodic table

main-group chemical element

(also, representative chemical element) chemical element in columns 1, 2, and 12–xviii

metal

chemical element that is shiny, malleable, good usher of heat and electricity

metalloid

element that conducts rut and electricity moderately well, and possesses some properties of metals and some backdrop of nonmetals

noble gas

(also, inert gas) element in group 18

nonmetal

element that appears boring, poor usher of oestrus and electricity

period

(likewise, serial) horizontal row of the periodic tabular array

periodic police

properties of the elements are periodic function of their atomic numbers.

periodic table

table of the elements that places elements with like chemical backdrop close together

pnictogen

element in group 15

representative element

(also, principal-group element) element in columns ane, ii, and 12–18

series

(too, menstruum) horizontal row of the flow tabular array

transition metallic

element in columns 3–xi

Solutions

Answers to Chemical science End of Affiliate Exercises

1. (a) metallic, inner transition element; (b) nonmetal, representative chemical element; (c) metal, representative element; (d) nonmetal, representative element; (e) metal, transition element; (f) metal, inner transition metal; (g) metal, transition metal; (h) nonmetal, representative element; (i) nonmetal, representative element; (j) metal, representative element

3. (a) He; (b) Be; (c) Li; (d) O

5. (a) krypton, Kr; (b) calcium, Ca; (c) fluorine, F; (d) tellurium, Te

vii. (a) [latex]_{11}^{23}\text{Na}[/latex]; (b) [latex]_{54}^{129}\text{Xe}[/latex]; (c) [latex]_{33}^{73}\text{Every bit}[/latex] ; (d) [latex]_{88}^{226}\text{Ra}[/latex];

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Source: https://iu.pressbooks.pub/openstaxchemistry/chapter/2-5-the-periodic-table/

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