Periodic Trends The Periodic Law Classification of Elements Electron Configurations in Groups Trends in Atomic Size Trends in Energy

Mendeleev’s Periodic Table Dmitri Mendeleev arranged the elements in his periodic table in order of increasing atomic mass. The periodic table can be used to predict the properties of undiscovered elements. Henry Moseley updated Mendeleev’s design by ordering elements by atomic number, rather than atomic mass.

The Periodic Law In the modern periodic table, elements are arranged in order of increasing atomic number. In the modern periodic table, the elements are arranged in order of increasing atomic number. Interpreting Diagrams How many elements are there in the second period?

The Periodic Law The periodic law: When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties. The properties of the elements within a period change as you move across a period from left to right. The pattern of properties within a period repeats as you move from one period to the next.

Metals, Nonmetals, and Metalloids Metals, Metalloids, and Nonmetals in the Periodic Table One way to classify elements in the periodic table is as metals, nonmetals, and metalloids. Inferring What is the purpose for the black stair-step line?

Metals, Nonmetals, and Metalloids Metals are good conductors of heat and electric current. 80% of elements are metals. Metals have a high luster, are ductile, and are malleable.

Metals, Nonmetals, and Metalloids In general, nonmetals are poor conductors of heat and electric current. Most nonmetals are gases at room temperature. A few nonmetals are solids, such as sulfur and phosphorus. One nonmetal, bromine, is a dark-red liquid.

Metals, Nonmetals, and Metalloids A metalloid generally has properties that are similar to those of metals and nonmetals. The behavior of a metalloid can be controlled by changing conditions.

1. The modern periodic table has elements arranged in order of QUESTIONS 1. The modern periodic table has elements arranged in order of colors. melting and boiling points. increasing atomic mass. increasing atomic number.

2. Mendeleev arranged the elements in his periodic table in order of increasing atomic number. number of protons. number of electrons. atomic mass

3. Which one of the following is NOT a general property of metals? ductility malleability having a high luster poor conductor of heat and electricity

Squares in the Periodic Table The periodic table displays the symbols and names of the elements, along with information about the structure of their atoms. This is the element square for sodium from the periodic table. Interpreting Diagrams What does the data in the square tell you about the structure of sodium atoms?

Squares in the Periodic Table The background colors in the squares are used to distinguish groups of elements. The Group 1A (1st group) elements are called alkali metals. The Group 2A (2nd group) elements are called alkaline earth metals. The nonmetals of Group 7A (17th group) are called halogens. The nonmetals of Group 8A (18th group) are called noble gases

Squares in the Periodic Table In this periodic table, the colors of the boxes are used to classify representative elements and transition elements.

Electron Configurations in Groups The Noble Gases The noble gases has a full outer shell. This makes then generally nonreactive.

Electron Configurations in Groups The Representative Elements Elements in groups 1A through 7A are often referred to as representative elements because they display a wide range of physical and chemical properties. These elements have between 1 and 7 valence electrons in its outer shell.

Electron Configurations in Groups In atoms of the Alkali metals below, there is only one electron in the outermost level.

Electron Configurations in Groups In atoms of the Group 4A elements below, there are four electrons in the highest occupied energy level.

Transition Elements Transition Elements There are two types of transition elements—transition metals and inner transition metals. They are classified based on their electron configurations.

Transition Elements In atoms of a transition metal, the highest occupied s sublevel and a nearby d sublevel contain electrons. In atoms of an inner transition metal, (also called rare-earth metals) the highest occupied s sublevel and a nearby f sublevel generally contain electrons.

Transition Elements Blocks of Elements This diagram classifies elements into blocks according to sublevels that are filled or filling with electrons. Interpreting Diagrams In the highest occupied energy level of a halogen atom, how many electrons are in the p sublevel?

QUESTIONS 4. Which of the following information about elements is usually NOT included in a periodic table? color symbol atomic number atomic mass

5. An alkali metal would have in the highest occupied energy level an s2 electron. an s1 electron. p2 electrons. p6 electrons.

6. Which one of the following is incorrectly labeled? Ne, noble gas Cu, transition metal Ga, transition metal Cl, halogen

Trends in Atomic Size Group and Periodic Trends in Atomic Size In general, atomic size increases from top to bottom within a group and decreases from left to right across a period.

Trends in Atomic Size The size of atoms tends to decrease from left to right across a period and increase from top to bottom within a group. Predicting If a halogen and an alkali metal are in the same period, which one will have the larger radius?

Ions Cation When a sodium atom loses an electron, it becomes a positively charged ion. When a chlorine atom gains an electron, it becomes a negatively charged ion. Interpreting Diagrams What happens to the protons and neutrons during these changes?

Ions Anion When a sodium atom loses an electron, it becomes a positively charged ion. When a chlorine atom gains an electron, it becomes a negatively charged ion. Interpreting Diagrams What happens to the protons and neutrons during these changes?

Ions Some compounds are composed of particles called ions. An ion is an atom or group of atoms that has a positive or negative charge. A cation is an ion with a positive charge. An anion is an ion with a negative charge.

Summary of Trends Nuclear Charge Electronegativity Size of anions Ionic size Ionization energy Shielding Atomic Size Size of cations Decreases Constant Increases Decreases Increases Properties that vary within groups and across periods include atomic size, ionic size, ionization energy, electronegativity, nuclear charge, and shielding effect. Interpreting Diagrams Which properties tend to decrease across a period?

7. Which of the following sequences is correct for atomic size? Questions 7. Which of the following sequences is correct for atomic size? Mg > Al > S Li > Na > K F > N > B F > Cl > Br

8. Metals tend to gain electrons to form cations. gain electrons to form anions. lose electrons to form anions. lose electrons to form cations.

9. Which of the following is the most electronegative? Cl Se Na I