ATOMS

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• ATOMS ELEMENTS
• By F. Todd 2004

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ATOMIC MODELS

• John Dalton Model 1808
• Viewed the atom as a SOLID BALL
• Each element is made of its own unique atom.
• Atoms are not divisible

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• J.J.Thomson 1897
• Viewed atom as a positive charged sphere with
  negative particles embedded inside it.
• Example Plum pudding model/ Blueberry muffin

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• Rutherford Model 1911
• The atom is mostly empty space.
• Discovers positively charged nucleus with the
  Gold foil experiment.
• Electrons orbit nucleus in a random fashion

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Rutherfords Gold Foil experiment
Source http//www.mhhe.com/physsci/chemistry/esse
ntialchemistry/flash/ruther14.swf
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• Chadwick Model 1932
• Discovers the NEUTRON in the
• nucleus
• Nagaoko Model 1904
• Atom is positive at the center with electrons
  orbiting the center like planets orbiting the
  sun.

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• Bohr Model 1913
• Similar to Nagaoka model but electrons orbit
  nucleus in layers(shells).
• Electrons can jump between shells.

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• Modern Model-Cloud Model
• Electrons form a negatively charged cloud around
  the nucleus.
• Impossible to determine the exact location of the
  electrons at any one point in time.

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Atomic structure

• Nucleus- central core of the atom.
• Made of protons () and neutrons (0)
• Protons positive particles in nucleus
• Mass1 AMU (Atomic mass unit)
• (1gram 6 followed by 23 zeros of protons)
• They balance out the number of electrons in the
  atom.
• Identified by Rutherford
• Neutrons neutral particle found in the nucleus
• Mass 1AMU
• Identified by Chadwick in 1932

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Atomic structure

• Electron cloud -location outside of nucleus where
  the electrons are found
• Electrons- negatively charged particles
• Identified by J.J.Thomson in 1897
• They balance out the protons in the nucleus
• Mass1/1836 AMU (much much smaller than a proton
  but carries a powerful negative charge)
• Gives each atom its chemical characteristic
• Involved in chemical bonding
• Arranged in energy levels or shells
• First (called the K-shell)can hold 2 electrons
• Second (called the L-shell) can hold 8 electrons
• Third (called the M-shell) can hold 18 electrons
  if not a valence shell
• Fourth (called the N-shell) can hold 32 electrons
  

L
K
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• Valence electrons
• Electrons that are farthest away from the nucleus
• (located in the outermost energy level)
• Involved in chemical bonding
• K-shell can have up to 2 valence electrons.
• All other shells can hold a maximum of 8
  electrons if they are
• the outermost valence shell of the atom.

How many valence electrons does this atom
have?______
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Atomic structure

• Atomic number- Tells how many protons are located
  in the nucleus of an element.
• Example Hydrogen has an atomic number 1
• Therefore Hydrogen has 1 proton in its nucleus
• Also tells how many electrons are in the element.
• Therefore Hydrogen contains 1 electron in its
  cloud.

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Atomic structure

• Mass number The total number of protons and
  neutrons in the nucleus of an atom.
• Example Carbon has 6 protons and 6 neutrons
  therefore Carbons mass number 12.
• Atomic mass the average of all the isotopes of a
  particular element found in nature.
• Isotope atoms of the same element that have the
  same number of protons but different number of
  neutrons.

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CARBON 12 ISOTOPE
CARBON 14 ISOTOPE
How many protons are in this nucleus?_____ Neutron
s?____
How many protons are in this nucleus?_____ Neutron
s?____
6
6
6
8
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13 Al 26.98154

• 13
• 26.98154amu
• 27 amu

What is the atomic of Aluminum?_______ What is
the atomic mass of Aluminum?_______ What is the
mass number of Aluminum?_______

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How many protons are found in the
Aluminum?__ Electrons?_____ Neutrons?___________

• 13

• 27-1314

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ELEMENTS

• Element Facts
• Definition- an element is a substance made of the
  same kind of atoms that cannot be broken into
  anything other than itself by ordinary physical
  or chemical means.
• 113 elements(113, 115-118 questionable) 114
  was made and verified
• Organized in the periodic table based on
  properties
• 92 are naturally found in the universe
• 11 gases, 2 liquids (bromine and mercury), rest
  solids (metals, nonmetals, metalloids) at room
  temperature
• Elements after Uranium (atomic 92) have been
  made in the laboratory
• Represented by chemical symbols
• John Berzelenus (France 1800s started using
  symbols)

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USE THE PERIODIC TABLE FROM YOUR BOOK TO IDENTIFY
THE SYMBOL FOR THE ELEMENTS BELOW.
Ba
Cl
F
U
Pb
Zn
H
N
B
P
C
Hg
O
Mg
Ra
Li
S
W
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He
Ar
As
Co
Si
Rn
Ag
Ti
Ni
Na
Br
I
Al
Cr
Fe
Ba
Ne
Mn
Au
Ca
Cd
Sn
K
Cu