Download Notes on Atomic Structure atoms

Atoms
Elements vs. Compounds
 Elements can NOT be chemically broken
down to a simpler substance, compounds
can. (Ex. 2H2O  2H2 + O2)
 Most materials are MIXTURES of
elements and/or compounds
Law of Constant
Composition
 A given compound always contains the
same proportions (by mass and by
number) of its elements
 This means a given compound always
has the same composition, regardless of
where it came from.
Dalton’s Atomic Theory
 Elements are made of tiny particles
called ATOMS
 All atoms of a given element are
identical*****
 The atoms of a given element are
different from those of any other element
Atomic Theory Cont’d
 Atoms of one element can combine with atoms
of other elements to form compounds. A given
compound always has the same relative
numbers and types of atoms.
 Atoms are indivisible in chemical processes.
That is, atoms are not created or destroyed in
chemical reactions. A chemical reaction simply
changes the way atoms are grouped together.
Chemical Formulas
 A formula describes how a compound is
composed in terms of atoms (how many
and which)
How many of each atom are in:
 Na2CO3
 (NH4)3PO4
ATOMS
Make Up of the Atom
 Protons – (p+)
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Defines the element
Is the integer number on the periodic table
Have a positive charge
Has a mass of 1 amu (atomic mass unit)
How many protons does Carbon have?
How many protons does Iron have?
How many protons does Ununnilium have?
What element has 35 protons?
Make Up of Atoms
 Neutrons – (n0)
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Have no (neutral) charge
Have a mass of ~1 amu
Contribute to the total mass of an atom
Define the isotope of an atom
 How many neutrons does Carbon-12 have?
 How many neutrons does Carbon 14 have?
 How many neutrons does Uranium-238 have?
Make Up of Atom
 Electrons – (e-)
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Have a negative charge
Equal numbers as protons in NEUTRAL atoms
Gained, lost, or shared in CHEMICAL REACTIONS
Have a mass of 1/1836 th of a proton (negligible!)
How many electrons does Carbon have?
How many electrons does Fluorine have?
Make Up Of Atom
 Protons and Neutrons are in the center of the
atom.
 Electrons are whizzing around the nucleus
Empty Space
 There is a LOT of
empty space is in
between the nucleus
and the electrons
 If the nucleus was a
fly on the 50 yard line
of a football stadium,
the electrons would
be in the nosebleed
seats…
Chemical v. Nuclear
Reactions
 Chemical reactions:
 Electrons are involved (exchanged or shared)
 Atoms are rearranged, but stay as the same atom.
 What we will be studying most this year
 Nuclear reactions:
 Nuclei (protons and neutrons) are involved and
changed.
 Atoms become different elements by losing or
gaining protons.