PERIODICITY & PERIODIC LAW

Transcription

1 PERIODICITY & PERIODIC LAW Historic Developments in Periodic Table Periodic Law Key Features of the Periodic Table Key Features of Atoms Periodic Trends

2 Historic Developments of Periodic Table Dmitri Mendeleev was the first to arrange the known elements (his work was 1869) in a workable periodic table. He based his arrangement on grouping the elements by similar chemical & physical properties He arranged the elements in each group by increasing mass He left empty spaces in his table for not-yetdiscovered elements. See page 156 in textbook.

3 Historic Periodic Table Dalton s Elements This is really just interesting info; there s nothing here to know.

4 Historic Developments of Periodic Table Henry Mosely, used the latest scientific information and theories about the structure of atoms, and re-arranged the elements by increasing atomic number. We see here the beginning of the Representative vs. the Non- Representative elements (A vs B)

5 Historic Developments of Periodic Table The Periodic Table was relatively unchanged, except for the addition of discovered elements until about 1940 Glenn Seaborg won a Nobel Prize to suggest a series of elements (transuranium elements) that were either added into a longer periodic table or pulled out These series of elements are now known as the Lanthanide and Actinide Series

6 The Modern Periodic Table of The Elements

7 Modern Periodic Table Group 1 Alkali Metals Group 2 Alkaline-Earth Metals Group 17 Halogens Group 18 Noble Gases B, Si, Ge, As, Sb, Te Semi-metals, metalloids. Fe, Co, Ni The magnetic triad Cu, Ag, Au The coinage metals

8 Modern Periodic Table 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. This was the major contribution of Henry Moseley.

9 Modern Periodic Table Elements properties are periodic Some properties are at maximums at Noble Gases Some properties are at minimums at Noble Gases Some maximums and minimums occur at alkali metals and halogens There are exceptions within the Transition Metals

10 The Modern Periodic Table The periodic nature of the elements is based mostly upon. Electron configurations

11 The Modern Periodic Table

12 Modern Periodic Table Since the s and p orbital for any element comprise the valence shell, the s-block and p-block of the periodic table hold the representative elements. The representative elements as a full collection represent all of the different types of chemical & physical behaviors. The noble gases are generally NOT included as representative elements, since their valence shells are filled. Representative Elements

13 Modern Periodic Table The non-representative elements are called the Transition Metals The d-block are the transition metals and The f-block are the inner transition metals The electron energy levels being filled for these elements are under the valence shell, and the inner transition metals are filling energy levels inside the other transition metals energy levels. Transition Metals Inner Transition Metals

14 Atomic Mass Periodic Trends Increases down and to the right (this one is sort of Duh!) Atomic Radius Increases down the periodic table Because each period adds another layer of electrons (energy levels) The inner energy levels shield the attraction between protons & electrons Decreases from left to right Because the protons and electrons increase within the same energy level greater attraction, smaller radius.

15 Mass & Radius + +

16 Ionization Energy Ionization Energy The energy required to remove an electron from its orbit As atoms get smaller they hold electrons more tightly, so Ionization energy has an opposite trend to atomic radius

17 Ionization Energy Since most elements have more than one electron, they have more than one ionization energy 2 nd, 3 rd, 4 th ionization energies are always greater than the 1 st ionization energy But, something important happens in the s block

18 Ionization Energy For the alkali metals (group 1), after they lose the 1st electron, the remaining electrons have noble gas configuration So the 2nd ionization energy for alkali metals is much higher (see page 173) And the 3rd ionization energy for the alkaline-earth metals is much higher as well

19 Electronegativity A unit-less value that represents the ability of an atom to attract electrons in a chemical bond The greater the electronegativity, the more strongly the electrons are pulled around that atom Electronegativity is greatest among small non-metals and is weakest among large metals.

20 Trend for Ionization Energy & Electronegativity Don t include Noble Gases in en - trend.

21 General Chemical Reactivity This trend line is two lines but not really Since metals and non-metals behave very differently The nature of metals is to donate electrons So large metals with s 1 or s 2 configuration are the most reactive The nature of non-metals is to receive electrons So small non-metals with p 4 or p 5 configuration are most reactive

22 General Chemical Reactivity - Non Metals Smaller atoms and molecules move more and faster than larger atoms and molecules (assuming same T) Since smaller non-metals are also moving faster, AND they are better at receiving electrons, they are, generally, more reactive than larger non-metals

23 General Chemical Reactivity - Metals Larger metals move more slowly than smaller metals, BUT are better at donating electrons, so. Metal reactivity is not governed by a general trend, but has been empirically determined Metals activity series.(see page 333), so

24 Reactivity Trend Boron & Silicon would be more non-metallic while Antimony & Tellurium would be more metallic. This trend is the activity series for non-metals?

25 General Chemical Reactivity Alkali Metal Trend? Since Lithium is bigger than oxygen and hydrogen (and close to the same size as the water molecule).so, The reactivity trend shown in the Alkali Metal reacting with water video is based more on. The ability of those metals in losing their valence electrons.

26 General Chemical Reactivity - The Semi-Metals Smaller semi-metals are better at acting like non-metals than they are at acting like metals Bigger semi-metals are better at acting like metals than they are at acting like nonmetals. So they are generally moderately reactive, but it depends.

27 General Chemical Reactivity These trends are the weakest of the trends (except for the activity series of metals; that s based on hard measured evidence) This weakness is because reactivity is subjective reactive with WHAT? So it depends a little on what these elements are reacting with

28 Best Web Site for Atomic Data for Periodic Family Project Web Elements