The Periodic Table

content  i. Dimitri Mendeleev's periodic table  ii. The modern periodic table  iii. Families of the periodic table  iv. Periodic trends  v. Ionization energy  vi. Ions  vii. Valence electrons  viii. Electronegativity  ix. Lewis’s Octet rule  x. Credit  i. Dimitri Mendeleev's periodic table  ii. The modern periodic table  iii. Families of the periodic table  iv. Periodic trends  v. Ionization energy  vi. Ions  vii. Valence electrons  viii. Electronegativity  ix. Lewis’s Octet rule  x. Credit

Dmitri Mendeleev: Father of the Table HOW HIS WORKED… Put elements in rows by increasing atomic mass. Put elements in columns by the way they reacted. SOME PROBLEMS… He left blank spaces for what he said were undiscovered elements. He broke the pattern of increasing atomic mass to keep similar reacting elements together.

The Current Periodic Table Now the elements are put in rows by increasing ATOMIC NUMBER The horizontal rows are called periods and are labeled from 1 to 7. The vertical columns are called groups are labeled from 1 to 18.

Families on the Periodic Table Columns are also grouped into families. Families may be one column, or several columns put together. Families have names rather than numbers.

Hydrogen Hydrogen belongs to a family of its own. Hydrogen belongs to a family of its own. Hydrogen is a diatomic, reactive gas. Hydrogen is a diatomic, reactive gas.

Alkali Metals  1 st column on the periodic table (Group 1) not including hydrogen.  Very reactive metals, always combined with something else in nature (like in salt).

Alkaline Earth Metals Second column on the periodic table. (Group 2) Reactive metals that are always combined with nonmetals in nature. Several of these elements are important mineral nutrients (such as Mg and Ca)

Metals vs. Nonmetals  Metals are shiny, good conductors of heat and electricity, malleable, ductile, and form cations (positive ions, loss of electrons) during chemical change.  Nonmetals are not shiny. They are poor conductors, brittle. They frequently form anions (negative, gain of electrons) in chemical changes.

Transition Metals Transition Metals Elements in groups 3-12 Elements in groups 3-12 Less reactive harder metals Less reactive harder metals Includes metals used in jewelry and construction. Includes metals used in jewelry and construction.

Metalloids  Metalloids have some characteristics of both metals and nonmetals. They are B, Si, Ge, As, Sb, Te, Po, At.

Halogens Elements in group 17 Elements in group 17 Very reactive, volatile, diatomic, nonmetals Very reactive, volatile, diatomic, nonmetals Always found combined with other element in nature. Always found combined with other element in nature. (CHLORINE)

The Noble Gases AKA Inert Gases AKA Inert Gases Elements in group 18 Elements in group 18 VERY unreactive, monatomic gases VERY unreactive, monatomic gases Have a full valence shell. Have a full valence shell.

Periodic Trends Moving left to right across a period, atomic radius usually decreases. This occurs because each successive element has an added proton and electron which causes the electron to be drawn closer to the nucleus. This decrease in atomic radius also causes the ionization energy to increase when moving from left to right across a period. The more tightly bound an element is, the more energy is required to remove an electron. Similarly, electronegativity will increase in the same manner as ionization energy because of the amount of pull that is exerted on the electrons by the nucleus.

Summary of Periodic Trends

Ionization energy Energy required to overcome the attraction of the nuclear charge and to remove an electron from a gaseous atom.

Ions + positive ions - cations - always smaller than the neutral atom from which they form because loss of outer-shell electrons result in increased attraction by nucleus for the fewer remaining electrons.  negative ions - anions - always larger than the neutral atom because effective nuclear attraction is less for increased number of electrons

Group trends v.s period trends Ionic radii increase as moving down each group Gradual decrease in size for both cations and anions as moving from left to right

electronegativity The tendency for atoms of the element to attract electrons when they are chemically combined with atoms of another element They are calculated and expressed in arbitrary units called Paulings

Pauling electronegativity scale Noble gases do not form any compund so omitted in the scale Electronegativiy of representative elments(Group A elements) increases as moving from left to right Metallic elements= low Non-metallic elements= high Most electronegative: Fluorine- 4.0 Least electronegative: Cesium- 0.7 Elctronegativity values help predict type of bonding between atoms in compounds.

Valence electrons Electrons in the highest occupied enegy level of an element’s atoms The number of valence electrons largely determines the chemical properties of an element Therefore: elements within each group behave similarly because they have the same number of V.e-

Valence electrons The number of valence electrons is the same as the group number of the element. (eg.Gr 1A elements has 1 V.e-) EXCEPTION: GR 0 (noble gases)- Helium has 2 V.e- and all others have 8. V.e- are usually the only electrons used in chemical bonding so only V.e- are shown in electron dot structures.

Octet rule  Gilbert Lewis, 1916  In forming compounds, atoms tend to achieve the electron configuration of a noble gas ( n s 2 n p 6 )  Atoms of metallic elements tend to lose V.e -, leaving complete octet in next lowest energy level  Atoms of some non-metallic elements tend to gain e - or to share e - with another non-metallic element to achieve a complete octet.  Gilbert Lewis, 1916  In forming compounds, atoms tend to achieve the electron configuration of a noble gas ( n s 2 n p 6 )  Atoms of metallic elements tend to lose V.e -, leaving complete octet in next lowest energy level  Atoms of some non-metallic elements tend to gain e - or to share e - with another non-metallic element to achieve a complete octet.

Credits Powerpoint presentation designed by: Victoria Gotay and Mengyi Xu Content sources: Chemistry Chemistry, fifth edition, Addison-Wesley publications Images and graphs souces : Powerpoint presentation designed by: Victoria Gotay and Mengyi Xu Content sources: Chemistry Chemistry, fifth edition, Addison-Wesley publications Images and graphs souces : THANK YOU !!!