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What is the World made of? What is holding it together?. The Greek thinker Aristotle classified the fundamental elements as fire, air, earth, and water.
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The Elements: Forged in Stars
The Origin of the Elements
Electrons have such a small mass compared to protons and neutrons we say electrons have no mass – but really they do.
p+ = 1 amu amu – atomic mass unit
n = 1 amu 1/12 of a Carbon -12
e- = 0 amu
p+ = positive charge nucleus
n = no charge nucleus
e- = negative charge cloud
Murray Gell-Mann found the name "quark" in the book "Finnegan's Wake" by James Joyce. The line "Three quarks for Muster Mark..." Gell-Mann received the 1969 Nobel Prize for his work in classifying elementary particles.
Quarks: Inside the Atom
Fermilab – National Particle Accelerator Lab Chicago IL
Can you figure out which cork stands for which quark?
EXTRA CREDIT: Find out what a neutrino is & why it’s important to SD
Always the smaller of the 2 #
Always a whole # (no decimals)
= number p+
Always the BIGGER of the 2 #
Usually a decimal
= # p+ & n
Number of atoms
Li Na K Cl Br I7 23 39 35 80 127
Ca Sr Ba (40 + 137) ÷ 2 = 8840 88 137
Dobereiner proposed the Law of Triads:
The middle element in the triad (group of 3 elements) had atomic weight that was the average of the other two members
Law of Octaves
John Newlands proposed The Law of Octaves:
When elements are arranged in increasing atomic mass the 1st & 8th elements exhibit similar behavior. This behavior repeats in a periodic fashion
Little attention was paid to Newlands work because he linked his finding to music.
In 1869 & 1871
“I began to look about and write down the elements with their atomic weights and typical properties, analogous elements and like atomic weights on separate cards, and this soon convinced me that the properties of elements are in periodic dependence upon their atomic weights.”--Mendeleev, Principles of Chemistry, 1905, Vol. II
IUPAC 1 2 13 14 15 16 17 18
American 1A 2A 3A 4A 5A 6A 7A 8A
European IA IIA IIIB IVB VB VIB VIIB VIIIB
3 4 5 6 7 8 9 10 11 12
3B 4B 5B 6B 7B ----8B----- 1B 2B
IIIA IVA VA VIA VIIA -------VIIIA------ IB IIB
Group or Family – Vertical columns on the PT
Elements in a groups have similar properties
Period – Horizontal rows on the PT
LEFT of the Zigzag Line
Bohr deduced that:
The Lewis electron-dot diagrams focus on the electrons in the highest energy level in the atom, the valence electrons.
Valence electrons are the electrons that participate in chemical reactions.