Download What is the history of chemistry and elements

Ch. 7 Notes: Atomic Structure and the Periodic Table
EQs
1.How are elements named?
2. What is the structure of an atom?
3. How are ions formed from atoms?
History
 2400 year ago Greek philosophers proposed that
everything was made of four basic substances –
air, water, fire, and earth.
 Today chemists know that there are 100+ basic
substances, or elements.
 Everything on Earth is made of these elements
or combinations with other elements in
compounds.
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Lavoisier published the 1st modern chemistry
textbook in 1789.
He named 33 elements, and said chemists
should always try to break down elements into
simpler substances.
From regions they’re found in, named after
scientists, or from Greek words
Some element’s symbols are the first letter of
it’s name (hydrogen – H, sulfur – S)
Symbols can also be the first letter and another
within the word. Some come from the name of
the element in Latin or Greek.
Protons – positive charge, in nucleus
Neutron – no charge (neutral), in nucleus
Electron – negative charge, move around
outside of nucleus
Atoms are extremely small.
Atomic Number – number of protons in an
atom’s nuleus
Determines the identify of the atom
Atomic Mass – total number of protons and
neutrons in nucleus
Ch. 7 Notes: Atomic Structure and the Periodic Table
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Elements always have the same number of
protons, but sometimes have different numbers
of neutrons or electrons
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Isotopes – atoms of the same element that have
a different number of neutrons
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Positive ion – formed when an atom loses an
electron causing the ion to have a positive
charge (has fewer electrons making it smaller
than the atom)
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Negative ion – formed when an atom gains an
electron causing the ion to have a negative
charge (has more electrons making it bigger
than the atom)
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Negative ions are represented by placing a
minus sign at the element’s symbol. Positive
ions are represented with a + sign to the upper
right of the of the symbol.
Ch. 7 Notes: Atomic Structure and the Periodic Table
1. How is the periodic table
organized?
2. How are properties of elements
shown in the periodic table?
Mendeleev’s Periodic Table
• Elements organized by similarities
• 1860’s he arranged elements according to
physical and chemical properties
• Arranged table so that atomic masses increased
moving down each vertical column
• Predicted new elements where empty spaces in
the pattern of periodic table
Modern Periodic Table
• Organized by properties and atomic number.
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Similar properties found in columns not rows.
Elements arranged by atomic number.
Reading the Periodic Table
• Atomic number – the number at the top
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Chemical symbol – abbreviation for element’s
name
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Name of Element – written below symbol
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Atomic mass – average mass of the isotopes of
element
Groups and Periods
• Columns – group (family), similar physically
• Horizontal rows – period, elements change in
predictable ways from one side of period to the
other
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Bohr Model of arrangement of electron shells.