Deciphering the Code of the Universe: Simple Keys to
Understanding and Interpreting the Periodic Table of Elements
Slide 2
The Periodic Table of Elements Element: atoms of a class of
substances that cannot be separated into simpler substances by
normal (natural) chemical processes. Each element has the same
number of protons (Atomic Number) in their nucleus. For several
reasons, atoms sharing the same atomic number (elements) almost
always share the same chemical properties: a property or
characteristic of a substance that is observed during a reaction in
which the chemical composition or identity of the substance is
changed. Ex. Sodium (Na-atomic number 11) has has combustibility-
meaning that it tends to ignite fire in chemical reactions. to
ignite fire in chemical reactionsto ignite fire in chemical
reactions Atoms of the same element can have different bonding
structures and physical properties. Ex. 1: Isotopes of Carbon (6)
have different numbers of neutrons, but still share atomic numbers.
This results in differing In the 19 th century, many scientists
began isolating various different elements. The created a need for
chemists to be able to better organize elements, resulting in
Dmitri Mendeleevs Periodic Table.
Slide 3
The Periodic Table of Elements Periodic: Appearing or occurring
at regular cyclic and repeating intervals. This means that the
periodic table is based of patterns (cycles) of repeating intervals
of elements with similar properties. The columns on the Periodic
table are called groups. Each group shares the same number of
valence electrons, giving them similar properties The rows on the
periodic table are called periods. Atomic number increases across a
period, and each period has the same number of orbitals.
Slide 4
PERIOD GROUP Atomic Number Symbol/ Name Atomic Mass
Slide 5
Atomic Radius Atomic Radius: Electrons exist in a
proportionately large probability cloud around the nucleus of every
atom. The atomic radius describes the size of the atoms cloud, and
it decreases moving right across a period, and increases moving
down a group. What it means: Every one knows that opposite forces
attract. The electrostatic attraction between the positive nucleus
and the negative electrons decreases as the distance between the
two increases. This means that elements with a higher atomic radii
are more likely to give up their valence electrons because of
reduced attraction with their nuclei.
Slide 6
Atomic Mass Atomic Mass (IAUPC AMU Definition): The mass of an
atom measured in AMUs (Atomic Mass Units). 1 AMU mass of 1 nucleon
(proton or neutron). Therefore, to find the Atomic Mass in AMUS,
simply add the number of protons (Atomic Number) to the number of
neutrons. Atomic masses of elements that have differing numbers of
neutrons (isotopes) are averaged. Atomic mass tends to increase
across a period and down a row. Atoms (esp. metals) with greater
atomic masses tend to be highly radioactive, poisonous or contain
other unique properties. Atomic Masses with large repeating
decimals have many differing isotopes.
Slide 7
Reactivity (Bonding) I Atoms of elements can combine using
electrons to produce larger chains or groups of atoms call
compounds. Bonding generally results in one of two types: 1.)
Covalent Bonds=A covalent bond is is a chemical bond that results
in the sharing of electrons between atoms. Ex. H 2 O 2.) Ionic
Bonds= Chemical bond in which electrons are stolen from atoms. Ex.
NaCl
Slide 8
Reactivity II Reactivity: behavior in which atoms forms new
substances by addition or subtraction of atoms from another
reactant or reactants. Several Factors influence reactivity,
including: atomic mass, atomic radius, atomic number,
electronegativity, ionization energy and (sometimes) electron
affinity. Electronegativity: The tendency of an atom to attract
electrons to itself. Increases across a period, and decreases down
a group. Greater the electronegativity, the greater the reactivity.
Ionization Energy: The amount of energy required to remove an
electron from an atom. Increases across a period, and decreases
down a group. Greater the ionization energy, less reactive (perhaps
ionic only?) the substance.
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Metallic Character Metallic Characteristics: Summary of Common
Properties: They are/have generally: Shiny (Luster), Solids at room
temperature (excp. Hg/80), High melting points, High densities, Low
ionization energies, Low electronegativities Large atomic radii,,
Malleable, Ductile, Thermal conductors Electrical conductors.
Metals are the most numerous elements on the periodic table.
Metalloids have semi-metallic properties, and often have
technological uses. Most non-metals are gaseous at room
temperature, and bond to eachother to create a covalent bond.
Metals bond to nonmetals in ionic bonding. Ex. Fe 2 O 3
Slide 10
Radioactivity Radioactive decay: the process by which an atomic
nucleus of an unstable atom loses energy by emitting ionizing
particles. Ex. Uranium(92) is highly radioactive, and was used in
the development of the atom bomb. Nuclei of Elements with atomic
numbers > 83 (Bismuth) are highly unstable, and begin
radioactive decay by the emission of 2 protons and 2 neutrons
(helium nucleus/alpha particle), an electron (beta emission) or a
highly dangerous gamma ray. Because of this emission, radioactive
elements continue decaying until the reach a stable nucleus. Ex.
When Polonium (Po/84) emits 2 beta particles, what element will it
become? Is it stable? What is its new atomic mass?
Slide 11
The Key to the Code Part II: Groups and Families
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Group 1/ Alkali Metals All of the Group 1 elements except
Hydrogen: Lithium, Sodium, Potassium, Rubidium, Cesium and
Francium. Hydrogen is often classified in its own family, because
it is not truly a metal. Alkali Metals are fun to through in lakes,
because they react fiercely with water in an explosion. Alkali
metals are very soft silvery metals that must be stored and handled
with caution due to their reactivity. Readily give up their only
valence electron (low ionization energy) to form cationic bonds
(become more positive).
Slide 13
Group 2/ Alkaline Earth Metals Beryllium, Magnesium, Calcium,
Strontium, Barium, Radium. React similarly to Alkali Metals, except
slightly less violently. Low ionization energy, readily give up two
valance electrons to form cations.