Periodic Table. September 22, Periodic Table.notebook

Transcription

1 Grab your notebooks off the lab table and copy down the EQ's Unit 4 Periodic Table Essential Questions: 1. Why are elements placed in a particular period or group on the periodic table? 2. Which elements on the periodic table are metals, nonmetals, metalloids, representative elements, transition elements, alkali metals, alkaline earth metals, halogens, and noble gases? Periodic Table Modern Periodic Table Arrangement Arranged according to INCREASING ATOMIC # WHY? > Elements with similar properties fall in the same column Periods: Horizontal rows (1-7) Groups (Families): Vertical columns (1-18 or 1A-8A and 1B-10B) Groups/Families continued... Representative elements are found in 1,2 and (or 1A-8A) all main group elements in the same group have: > same number of valence electrons > same oxidation number > similar chemical properties METALS, NON-METALS AND METALLOIDS 1

2 Representative Elements Found in groups 1, 2 and (1A- 8A) Group 1: Alkali Metals > one valence electron > soft, silvery metals, easily cut with a knife > very reactive, especially with air and water Group 2: Alkaline-earth metals > two valence electrons > harder, slightly less reactive & higher melting points A B C a) The rxn. of potassium with water. (b) The rxn. of calcium with water. These photos illustrate that group 1 metals tend to be more reactive than group 2 metals. (c) The reaction of sodium metal and chlorine gas is very exothermic. Elements in groups 1 and 2 are very active (reactive) metals. Metals in group 1 are more reactive than metals in group 2 (because group 1 metals have lower ionization energies). Alkali metals are too reactive to be found free in nature they are always combined with some other element (ex: NaCl). Alkaline earth metals are less reactive than alkali metals, but still too reactive to be found as free elements in nature. More representative Elements: Group 17 (7A) > Halogens most reactive non-metals «B/C they have high electronegativies and only need one electron to fill their octets «Halogens often react w/metals to form salts Na (s) + Cl 2(g) NaCl (aq) More representative Elements Group 18 (8A) > Noble Gases (AKA Inert Gases) Least reactive of all elements b/c they have a full outer shell Ex: Helium Transition Elements Elements in d-block AKA transition metals Includes groups 3-12 (1B-10B) Metals with metallic properties harder, denser, less reactive & higher melting poitns (expect for mercury) than groups 1&2 F-Block Elements: Neither representative nor transition elements Lanthanides: top row > AKA Rare Earth Elements Actinides: Bottom Row > most are synthetic but all are unstable and radioactive 2

3 Lets see it in ACTION! table Please put your PT Timelines on the back lab table over lab station 6. Have your PT Trends Straw lab out & ready, when the bell rings we will begin assembling our PT Trends! UNIT 4 EQ's PERIODIC TABLE TRENDS > How do you explain the trend for increasing radius of atoms or ions on the PT? > How do you explain the trend for ionization energy of elements on the PT? > How do you explain the trend for electronegativity of elements on the PT? Atomic Radius Periodic Table Trends 1/2 the distance between the nuclei of two covalentlybonded atoms Within a group: increases down a group Within a period: decreases across a period > WHY? adding a proton and an electron each time you move element to the right, added electrons are in the same energy level more protons = stronger pull on the electrons in that energy level, thus pulling them in tighter. Ionic Radius Ions: atoms or groups of atoms with a positive or negative charge > Cation: Postively charged ion (loss of electron) > Anion: Negatively charged (formed by gaining electrons) 3

4 Ionic Radius Continued... Ionic Radius ½ the diameter of an ion in an ionic compound Within a period: decreases from left to right but resets when transitions from non-metals (anions) to metals (Cations) Within a group: increases down a group Ionization Energy Minimum amount of energy required to strip away one electron from an atom of that element IN THE GASEOUS STATE Within a period: increase across a period group 1 has the lowest ionization energy reflection of atomic radius Within a group: decreases down a group Electronegativity The ability of an atom to attract electrons in a chemical bond > Remember the goal for all atoms is to be STABLE Noble Gasses are the most stable elements b/c they have a full octet Most electronegative is flourine Within a period: increases left to right Within a group: decreases down a group Electron Affinity the energy change associated with adding an electron to an atom IN ITS GASEOUS STATE Generally become more negative left to right across the periodic table 4

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