The document discusses the structure of atoms and the periodic table. It describes subatomic particles like protons, neutrons, and electrons. Atoms are made up of a nucleus containing protons and neutrons, surrounded by electrons. The periodic table organizes elements based on their atomic structure, including the number of protons and electrons. Elements are grouped according to their chemical properties, which depend on the number of electrons in their outer shell. The periodic table illustrates recurring trends in how elements behave and has helped explain atomic structure.

1. Back to the macroscopic world

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3. Week 3a
 Nuclear fusion within the Sun:
• Proton: positively charged, found in nucleus of the atom
• Neutron: neutral, found in nucleus of atom
• Positron: positive charge, antiparticle of electron
• Neutrino: neutral, interacts only weakly, small mass
• Gamma ray: highly-energetic photon
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5. Hydrogen Helium Carbon
Proton Alpha Produced in Beta decay
particle supernovae
Nuclear fusion in the sun
and early big bang
nucleosynthesis 3 minutes
H+H  He
Alpha decay
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7.  99 % consists of:
 Oxygen
 Carbon
 Hydrogen
 Nitrogen
 Calcium
 Phosphorus
 98 % of matter in the
universe is hydrogen
and helium
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8.  Atoms are neutral
 Number of electrons equals number of protons
 Nucleus consists of protons and neutrons in
(approximately) equal numbers
 Atomic number (Z): number of protons
 Mass number (A): number of p+n
 Number of neutrons (N=A-Z) may vary: isotope
6p+6n 6p+7n 6p+8n
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9. (99,3 %) (0.7 %)
 Isotopes have similar
chemical properties.
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10. Atomic number, Z
Atomic weight (close to A)
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11. Russian
chemist Dmitri
Mendeleev in 1869
Illustrates recurring
("periodic") trends in
the properties of the
elements
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13.  Bohr’s model:  Nucleus has internal
structure:
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14.  Build up of the periodic table
based on few simple physical principles:
 Total number of electrons such that atom is
neutral.
 Electrons in discrete orbits, as in Bohr’s model.
 Orbit has “quantum number”. Determines:
 Energy
 Size of the orbital
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15.  Each orbital specific number of electrons:
 Pauli exclusion principle: no two electrons in the
same state. At most two electrons in each orbital.
 There are suborbitals, wich give two extra
quantum numbers
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16. Total:
: s-orbital. Max: 2 electrons
: p-orbital. Max: 6=2x3 electrons
: d-orbital. Max: 10=2x5 electrons
: f-orbital. Max: 14=2x7 electrons
• The quantum states are called orbitals.
• States with the same are called shells (have the same energy).
• Each orbital has electrons, hence:
 shell can host electrons
 shell can host electrons
 shell can host electrons, etc.
• This should give the length of each row of the periodic table (2,8,18, etc.).
• There are exceptions due to screening of electrons. The actual lengths are
(2,8,8,18, etc.)
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17.  The Periodic Table is based on the
observation that an element's chemical
properties depend on the number of
electrons in its outer shell.
 You can count to see how many electrons are
in the outer unfilled shell. Elements with the
same number of electrons in their outer shell
are grouped together.
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20. Halogens:
• Highly reactive, harmful or lethal to biological organisms.
• Reactivity due to the atoms being highly electronegative. They can gain an
electron by reacting with atoms of other elements.
• Fluorine one of the most reactive elements, attacking otherwise inert
materials such as glass. Corrosive, highly toxic gas.
• Once it does react with something, it bonds so strongly that resulting
molecule is very inert and non-reactive. For example, Teflon is fluorine
bonded with carbon.
• Chlorine and bromine used as disinfectants for drinking water, swimming
pools, fresh wounds, dishes, and surfaces. They kill bacteria and
microorganisms.
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21.  Atoms (or molecules) in which number of
electrons does not equal number of protons.
 Electrically charged.
 : has lost one electron.
 : has gained one electron.
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22.  The periodic table is the alphabet or genetic
code in which we can write “words”.
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23.  Atoms  Letters
 Periodic table  Alphabet
 Molecules  Words
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24. Next level of complexity: the Questions ofScience, fall 2012. SdH, AUC
Big
words in chemistry (molecules) become the letters of biology.
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26.  Subatomic particles
 Atom: nucleus and electrons. Strong and
electrical force.
 Molecules. Periodic table. Electrical force.
 Emerging: van der Waals forces between
molecules.
 Substances, tissues. Electrical force.
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