The Periodic Table

The Big Questions Who developed the first modern periodic table? How did he organize it, and how does this differ from the organization of the P. T. today? What are some ways in which we group elements on the P. T.? What does this tell us about the atom’s structure?

The First Modern P. T. Developed in 1869 by Dmitri Mendeleev. Russian chemist and inventor. Arranged elements according to inc. atomic mass and periodicity. Periodicity – tendency of elements to repeat properties. Example: Lithium is a metal that reacts explosively with H 2 O. This property is repeated in Na, then again in K, and so on...

Dmitri Ivanovich Mendeleev

The First Modern Periodic Table

The First Modern P. T. DM noticed there were “holes” where no known element would fit. Guessed that these holes represented undiscovered elements. Made predictions about their properties. When discovered, these elements matched their predicted properties.

Periods (Rows) Periods – horizontal rows of elements. All elements on a period have the same number of energy levels.

Periods How many energy levels would you expect to find in atoms from the 4 th row? The 5 th row?

Families of Elements Families – columns or groups. Elements in a family have similar chem. properties. Also have same no. of valence e -. Coincidence? (No.)

Ions Atoms can lose or gain electrons. Ion – an atom that has become charged by gaining or losing electrons. Cation – positive ion (lost e - ) Anion – negative ion (gained e - )

Ions Gain 1 e - C-C- 6 p + 7 e - C 6 p + 6 e - Lose 1 e - C+C+ 6 p + 5 e -

The Octet Rule Atoms tend to gain or lose electrons so they can have 8 * valence electrons (same e - configuration as a noble gas). Why? 8 valence electrons = full s and p sublevel. Extremely stable configuration. * There are a few exceptions to this rule that we will discuss later.

Families of the Periodic Table Group 1A (1) Alkali metals 1 val. e - Form +1 ions. Group 2A (2) Alkaline earth metals 2 val. e - Form +2 ions.

Families of the Periodic Table Groups 3B – 2B (3 – 12) Transition metals Have variable val. e - Can form multiple cations. Group 3A (13) Boron group 3 val. e - Form +3 ions.

Families of the Periodic Table Group 4A (14) Carbon group 4 val. e - C and Si rarely form ions. All others: +2 or +4 Group 5A (15) Nitrogen group 5 val. e - Form –3 ions (except for bismuth: +3)

Families of the Periodic Table Group 6A (16) Chalcogens 6 val. e - Form –2 ions. Group 7A (17) Halogens 7 val. e - Form –1 ions.

Families of the Periodic Table Group 8A (18) Noble gases 8 val. e - (exc. He) Do not form ions.

Blocks s-block p-block d-block f-block

Metals, Metalloids, and Nonmetals Metals Majority of elements are metals Conductors of heat and electricity. Lose electrons (form + ions). Nonmetals About 16 elements. Insulators. Tend to gain or share e -

Metals, Metalloids, and Nonmetals Metalloids Between metals and nonmetals. Semi-conductors. Lose or share electrons.

Metals, Metalloids, and Nonmetals Metals Metalloids Nonmetals

Metallicity More MetallicLess Metallic More Metallic Less Metallic

Electron Configs. on the P. T. 1s 2s 3s 4s 5s 6s 7s 3d 4d 5d 6d 4p 5p 6p 7p 3p 2p 1s 4f 5f