Periodic Table and Its Trends Looking for the pattern with the elements

Metals Non-Metals Lab WWhat we some of the physical properties? chemical properties? WWhat are the characteristics of metals? Non-metals? WWhat are metalloids?

Made the periodic table to organize elements - Too many elements to memorize so they classified them. Periodic: regular, repeating pattern Mendeleev: made first periodic table 1800s First table was by increasing atomic mass: the average mass of one atom of the element Periodic Table

Mendeleev and table He made new rows each time properties repeated so the columns all had similar properties He left blank spots on table if properties didn’t match – all of his “blanks” have been discovered. The vertical columns are called groups The horizontal rows are called periods.

Modern Periodic Table Do Activity on pg ?

Trends in periodic table Many trends form in the periodic table when its organized by mass and atomic number: From your card periodic tables: plot of atomic number and Compounds formed: Atomic number vs. oxygen in compoundsAtomic number vs. oxygen in compounds

Periodic Table - Atomic Number The atomic number (on periodic table) shows the number of protons. o Its symbol is Z. o determines the identity of the element. o They are found in the nucleus o Atoms are electrically neutral so atomic number also shows number of electrons

Periodic table - Atomic Mass Atomic Mass/ Mass Number – o Symbol is A. o Mass only includes protons and neutrons because electrons are basically massless o Unit is the “atomic mass unit” (amu) or u Rule of Thumb: The number of protons determines the identity of the element Number of protons + neutrons

Isotopes and Atomic Number Scientists observed two kinds of neon atoms. o exactly alike chemically, but different in mass. o He called them isotopes 2 minute movie clip Isotopes - Atoms of the same element that differ in mass. o have the same number of protons but different numbers of neutron. o mass difference is due to the number of neutrons in isotope o Isotope names: element – mass eg Neon-20

Calculation /reading periodic table To get protons – look at periodic table for atomic number To get electrons - look at periodic table for atomic number Calculations : To get neutrons = mass number - atomic number To get Mass Number = protons + neutrons

Application Complete this supplement. Make a copy and place in your handouts and activities folder Supplement 2A You have 15 minutes to start this and ask questions.

Group 1: Alkali metals (not H) Group 2: Alkaline Earth Metals Groups 3-12: Transition metals Groups 13-15: No names/mixed groups Group 16: Chalcogens Group 17: Halogens Group 18: Noble Gases

Property trends Groups of elements have similar properties. All alkali metals (group 1) are silvery white and explosive, form XCl as their chlorides and X 2 O as their oxides o if Li forms Li 2 O with oxygen and Ca forms CaO, what is the formula for what Sr will form with Oxygen?

Property trends continued You can estimate a property of an element by averaging the values of the elements above and below it. eg: the density of silicon is 2.3 and the density of tin is 7.3. estimate the density of germanium. look on periodic table and observe that Ge is between Si and Sn within a group. Average the densities to get an estimate / 2 = 4.8

Group 1: Alkali metals (not H) – metals – have 1 electron on outer ring (1 valence electron) – gives it away to react and make + 1 ions Li 1+ Group 2: Alkaline Earth Metals - metals – have 2 electron on outer ring (2 valence electron) – gives it away to react and make + 2 ions, Mg 2+ Groups 3-12: Transition metals - give away electrons to react Groups 13-15: No names/mixed groups – no trend since metals and nonmetals are mixed in these groups Group 16: Chalcogens - nonmetals – have 6 valence electrons, react by gaining 2 electrons, O 2- Group 17: Halogens - nonmetals - have 7 valence electrons, react by gaining 1 electrons, F 1- Group 18: Noble Gases – nonmetals, have 8 valence electrons, DO NOT REACT Do A11 Supplement Electron pattern control element properties!!!