Introduction to the Periodic Table

History of Periodic Table Basic chemical elements known since prehistoric times Gold Silver Copper Why? Exist in native form (no processing needed). Easy to mine with simple tools.

History of Periodic Table Science has come along way since Aristotle’s theory of Air, Water, Fire, and Earth (300B.C.).

History of Periodic Table In 1669, 1st element discovered through scientific enquiry was phosphorus, P.

History of Periodic Table Hennig Brand (and later Robert Boyle) turned urine into P! Ewww! urine

Elements Song 1

So how and why are the elements organized as they are? History of Periodic Table Scientists have identified 90 naturally occurring elements, and created about 28 others (present total 118). So how and why are the elements organized as they are?

Elements in Periodic Table 3 Li 6.941

Li Information for Elements in the Periodic Table 3 6.941 Lithium Atomic Number Chemical Symbol Atomic number = protons an atom of that element has. The atomic number is unique to that element. No two elements have the same atomic number. 3 Li Chemical Name State of matter at room temperature Lithium 6.941 solid Atomic mass = protons and neutrons an atom of that element has (round to nearest whole number, so Li = 7)

Bohr Model of Atom C 6 Carbon Niels Bohr proposed the Bohr Model of the Atom in 1915. positively-charged nucleus orbited by negatively-charged electrons. Electrons orbit around the nucleus in different energy levels – lowest energy level nearest to nucleus. 1st energy level 2nd energy level

Li Subatomic Structure and Bohr Model of Atom 1 outer electron in 2nd electron shell 2 electrons (max.) in 1st electron shell 3 Li 7 Electron configuration for Li, 3 electrons = 2, 1

Kids to practice a few elements with magnetic Bohr model Try Helium (at # 2, mass 4) Beryllium (at # 4, mass 9) and magnesium (at # 12 mass 24)

How is reactivity of an element related to its position in the Periodic Table? All elements want to be stable and have full outer electron shell (2 electrons for 1st shell, 8 electrons for outer shells) Elements either try to lose an electron or gain one, whichever is easier energetically 9+ gain! F 3+ lose! Li

Reactivity Increases DOWN a group Reactivity decreases and then increases across period Non-reactive (inert) elements Reactivity Increases DOWN a group

Reactivity Increases going DOWN a group Single outer electron closer to positive nucleus than atoms further down the group with more electron shells – therefore not as reactive Li Lithium: 3P, 3e (2,1) 3+ Na Sodium: 11P, 11e (2, 8, 1) Single outer electron far from nucleus, shielded by “electron cloud” and easily lost, therefore Na more reactive than Li 11+

Li F B Lose 1 electron! Gain 1 electron! Reactivity decreases and then increases across period Li 5+ B F 5+ 3+ Lose 1 electron! Gain 1 electron! Needs 3 more electrons to get stable full shell of 8

Meet the Elements – They Might Be Giants

Your work! Na (element symbol) S L G Sodium (element name) 11 (atomic number) Na (11 N 12 e 11 t symbol) 23 (atomic mass) Sodium (element name)A Na (element symbol) Sodium (element name)   S L G P 11 N 12 e 11 Bohr model 2, 8, 1 electron arrangement

3 Li 7 lithium P 3 N 4 e 3 S L G Bohr model 2,1 Electron configuration