C HEMISTRY BOOK C H 3: INTRODUCTION TO THE PERIODIC TABLE IAT-RAK –LC2/ Gr.10 Teacher: Nagham Hussam

C H 3.1- DEVELOPMENT OF PERIODIC TABLE T HE S EARCH FOR A P ERIODIC T ABLE By 1860, scientists had already discovered 60 elements and determined their atomic masses. They noticed that some elements had similar properties. They gave each group of similar elements a name. Copper, silver, and gold were called the coinage metals. Lithium, sodium, and potassium were known as the alkali metals. Chlorine, bromine, and iodine were called the halogens. They wanted to organize the elements into a system that would show similarities while acknowledging differences. 2

D ÖBEREINER ’ S T RIADS In 1829, the German chemist J.W. Döbereiner classified some elements into groups of three, which he called triads. The elements in a triad had similar chemical properties, and their physical properties varied in an orderly way according to their atomic masses. 3

D ÖBEREINER ’ S T RIADS Triads show a relationship among the densities that is true for many triads. Density increases with increasing atomic mass 4

M ENDELEEV ’ S P ERIODIC T ABLE The Russian chemist, Dmitri Mendeleev, was a professor of chemistry at the University of St. Petersburg when he developed a periodic table of elements. Mendeleev later developed an improved version of his table with the elements arranged in horizontal rows. This arrangement was the forerunner of today’s periodic table. He showed that the properties of the elements repeat in an orderly way from row to row of the table. This repeated pattern is an example of periodicity in the properties of elements. 5

M ENDELEEV ’ S P ERIODIC T ABLE Periodicity is the tendency to recur at regular intervals. In order to group elements with similar properties in the same columns, Mendeleev had to leave some blank spaces in his table. He suggested that these spaces represented undiscovered elements. 6

T HE M ODERN P ERIODIC T ABLE 7

There are several places in the modern table where an element of higher atomic mass comes before one of lower atomic mass. This is because the basis for ordering the elements in the table is the atomic number, not atomic mass. The atomic number of an element is equal to the number of protons in the nucleus. 8

T HE M ODERN P ERIODIC T ABLE Atomic number increases by one as you move from element to element across a row. Each row (except the first) begins with a metal and ends with a noble gas. In between, the properties of the elements change in an orderly progression from left to right. 9

T HE M ODERN P ERIODIC T ABLE The periodic law: The statement that the physical and chemical properties of the elements repeat in a regular pattern when they are arranged in order of increasing atomic number. A group, sometimes also called a family, consists of the elements in a vertical column. Groups are numbered from left to right. 10

U SING THE PERIODIC TABLE C H.3.2 In the modern periodic table, elements are arranged according to atomic number. The atomic number tells the number of electrons it has. 11

C H.3.2 U SING THE PERIODIC TABLE The lineup starts with hydrogen, which has one electron. Helium comes next in the first horizontal row because helium has two electrons. Why does the first period have only two elements? Lithium has three. Only two electrons can occupy the first energy level in an atom. The third electron in lithium must be at a higher energy level 12

C H.3.2 U SING THE PERIODIC TABLE Eight electrons are added to Period 2 from lithium to neon, so eight electrons must be the number that can occupy the second energy level. The third period repeats the pattern of the second period. Each element has one more electron than its neighbor to the left, and those electrons are in the third energy level. 13

T HE MAIN GROUPS The main group elements are those in Groups 1, 2, 13, 14, 15, 16, 17, and 18. For the main group elements, the group number is related to the number of valence electrons. For elements in Groups 13, 14, 15, 16, 17, and 18, the second digit in the group number is equal to the number of valence electrons. Because elements in the same group have the same number of valence electrons, they have similar properties. 14

ALKALI METALS Group 1 Hydrogen is not a member, it is a non-metal 1 electron in the outer shell Soft and silvery metals Very reactive, esp. with water Conduct electricity Image:

ALKALINE EARTH METALS Group 2 2 electrons in the outer shell White and malleable Reactive, but less than Alkali metals Conduct electricity

BORON FAMILY Group 3 3 electrons in the outer shell Most are metals Boron is a metalloid

CARBON FAMILY Group 4 4 electrons in the outer shell Contains metals, metalloids, and a non- metal Carbon (C)

NITROGEN FAMILY Group 5 5 electrons in the outer shell Can share electrons to form compounds Contains metals, metalloids, and non- metals

OXYGEN FAMILY Group 6 6 electrons in the outer shell Contains metals, metalloids, and non- metals Reactive

G ROUP 17 Chlorine is in Group 17 and has 7 valence electrons. Throughout the periodic table, elements in the same group have similar chemical properties because the have the same number of valence electrons. The word halogen is from the Greek words for “salt former”. All are non-metals. Very reactive. 21

G ROUP 18 OR (8A) Group 18 elements have the maximum number of eight valence electrons in their outermost energy level. Group 18 elements are called noble gases. The noble gases, with a full complement of valence electrons, are generally un reactive. 22

G ROUPS COMMON NAMES Four groups have commonly used names: the Alkali Metals in Group 1. the Alkaline Earth Metals in Group 2,. the Halogens in Group 17. and the Noble gases in Group 18. Transition Metals from period 3 to 12(B Blok) 23

P HYSICAL S TATES AND C LASSES OF THE E LEMENTS The majority of the elements are Metals. They occupy the entire left side and center of the periodic table. Nonmetals occupy the upper-right-hand corner. Metalloids are located along the boundary between metals and nonmetals. Each of these classes has characteristic chemical and physical properties, so by knowing whether an element is a metal, nonmetal, or metalloid, you can make predictions about its behavior. 24

M ETALS With the exception of tin, lead, and bismuth, metals have one, two, or three valence electrons All metals except mercury are solids at room temperature; in fact, most have extremely high melting points. The elements in Groups 3 through 12 of the periodic table are called the transition elements. 25

TRANSITION ELEMENTS. The elements in Groups 3 through 12 of the periodic table are called the transition elements. All transition elements are metals. Some period 7 transition elements are synthetic and radioactive. In the periodic table, two series of elements, atomic numbers and , are placed below the main body of the table. The elements in these two series are known as the inner transition elements. Lanthanides: The first series of inner transition elements, because they follow element number 57, lanthanum. Because of their natural abundance on Earth is less than 0.01 percent, the lanthanides are sometimes called the rare earth elements. 26

TRANSITION ELEMENTS. The lanthanides consist of the 14 elements from number 58 (cerium, Ce) to number 71 (lutetium, Lu). The second series of inner transition elements, the actinides, have atomic numbers ranging from 90 (thorium, Th) to 103 (lawrencium, Lr). All of the actinides are radioactive, and none beyond uranium (92) occur in nature. 27

NONMETALS The nonmetals oxygen and nitrogen make up 99 percent of Earth’s atmosphere. Most nonmetals don’t conduct electricity, are much poorer conductors of heat than metals, and are brittle when solid. Many are gases at room temperature; those that are solids lack the luster of metals. Their melting points tend to be lower than those of metals. 28

P ROPERTIES OF METAL AND NONMETAL 29

M ETALLOIDS Metalloids have some chemical and physical properties of metals and other properties of nonmetals. In the periodic table, the metalloids lie along the border between metals and nonmetals. Silicon (Si) is probably the most well-known metalloid. Some metalloids such as silicon, germanium (Ge), and arsenic (As) are semiconductors. 30

SEMICONDUCTORS A semiconductor: is an element that does not conduct electricity as well as a metal, but does conduct slightly better than a nonmetal. The ability of a semiconductor to conduct an electrical current can be increased by adding a small amount of certain other elements. Silicon’s semi conducting properties made the computer revolution possible. Your television, computer, handheld electronic games, and calculator are electrical devices that depend on silicon semiconductors. All have miniature electrical circuits that use silicon’s properties as a semiconductor. The conductivity of a semiconductor can be increased by a process known as doping. 31

D EAR STUDENTS, The following link is the quizzes online for all the chapters in the Chemistry book. hill.com/sites/ /student_view0/self- check_quizzes.html Good luck 32