Alkali metals
Alkaline-earth
metalsTransition metals
Post-transition
metalsMetalloid
Nonmetals
Halogens
Noble gases
Lathanides
Actinides
Lower melting point Higher melting point Lower melting point
Group
Period
1 2 3 4 5 6 7
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Less metallic,
smaller atomic
radius, more
abundantMore metallic,
larger atomic
radius, less
abundantLess metallic, harder to remove
electrons, smaller atomic radiusMore metallic, easier to remove
electrons, larger atomic radiusEVERYTHING
WORTH
KNOWING
34 DISCOVERMAGAZINE.COM
DE
SIGN
UA
/SHU
T
T
ERSTO
CKWHETHER HUNG ON CLASSROOM WALLS,
put up in dorm rooms or screen-printed on
T-shirts, the periodic table of elements screams,
“Science!” like no other image. And why not?
At 118 members and counting, the table lists
every known chemical element, the (mostly)
immutable building blocks of all materials in
the universe.
But it’s not just a random list of elements. The
organization of the periodic table reveals an
element’s behaviors and characteristics: from
atomic size, density and abundance, to how it
would likely interact with others.
Take this opportunity to gaze upon the
periodic table and see for yourself some of its
hidden insights.
Serving up the elements.
BY BILL ANDREWS
Periodic
Tab le
Many periodic tables
include the atomic number
(number of protons) andatomic weight (which
depends on protons and
neutrons). Sometimes
they list the full name
of each element, but
often only include their one- or two-letter
symbol, nicknames that make complicated
chemical formulas more compact. If the
symbol doesn’t match the name (as in
Au for gold and Na for sodium), it’s likely
based on the element’s original Latin name
(aurum and natrium).
Elements in the same column often
share similarities, so chemists call these
groups. Roughly speaking, the farther to
the right a group is, the more electrons it
has ready to interact with other elements.
The first group, known as the alkali metals,
has just one such electron, easy to lose
when reacting with an element that has
more electrons, such as one from the 17th
group, the halogens. The noble gases, in
the last column, are so named because
they’re holding about all the electrons
they can, so they don’t react easily with
other elements — just as the noble houses
of old.
Rows in the periodic table are called
periods, and we currently have seven. They
list the elements in order of atomic number
before cutting off and continuing again in
a new row, repeating established patterns
of chemical properties. The tricky part in
constructing the table is knowing when
they cut off — or, equivalently, how many
columns (groups) to include in each row.
Elements 101
Everything is made up of atoms, and atoms are
made up of their own tiny particles: Electrons
flit semi-randomly around a central nucleus,
which is made up of neutrons and protons.
(Neutrons and protons are themselves made
up of other particles: quarks.) The number of
protons, also called the atomic number, defines
an element — alter that, and you’ve changed the
element itself.
How to Read the Table KEY^
Atom
Nucleus
Neutron
Proton
Quarks
Electron
atomic numberSymbol
name
atomic weight