Deciphering the Code
of the Universe:
Simple Keys to Understanding and Interpreting the
Periodic Table of Elements
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.
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 19th century, many scientists began isolating various different elements.
The created a need for chemists to be able to better organize elements,
resulting in Dmitri Mendeleev’s Periodic Table.
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.
PERIOD
Atomic
Number
Symbol/ Name
Atomic
Mass
GROUP
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 atom’s 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.
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.
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. H2O
2.) Ionic Bonds= Chemical bond in which electrons are
stolen from atoms. Ex. NaCl
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.
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. Fe2O3
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?
The Key to the Code
Part II:
Groups and Families
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).
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.