英文字典中文字典Word104.com

The Collaborative International Dictionary of English v.0.48 (gcide)

Periodic \Per`i*od"ic\ (p[~e]r`[-i]*[o^]d"[i^]k), a. [Pref. per-
iodic.] (Chem.)
Pertaining to, derived from, or designating, the highest
oxygen acid ({HIO4}) of iodine.
[1913 Webster] Periodic


Periodic \Pe`ri*od"ic\ (p[=e]`r[i^]*[o^]d"[i^]k), Periodical
\Pe`ri*od"ic*al\ (p[=e]`r[i^]*[o^]d"[i^]*kal), a. [L.
periodicus, Gr. periodiko`s: cf. F. p['e]riodique.]
1. Of or pertaining to a period or periods, or to division by
periods.
[1913 Webster]

The periodical times of all the satellites. --Sir J.
Herschel.
[1913 Webster]

2. Performed in a period, or regular revolution; proceeding
in a series of successive circuits; as, the periodical
motion of the planets round the sun.
[1913 Webster]

3. Happening, by revolution, at a stated time; returning
regularly, after a certain period of time.
[1913 Webster]

The periodic return of a plant's flowering.
--Henslow.
[1913 Webster]

To influence opinion through the periodical press.
--Courthope.
[1913 Webster]

4. Acting, happening, or appearing, at fixed or somewhat
variable intervals; recurring; as, periodical epidemics
[1913 Webster]

5. (Rhet.) Of or pertaining to a period; constituting a
complete sentence.
[1913 Webster]

{Periodic comet} (Astron.), a comet that moves about the sun
in an elliptic orbit; a comet that has been seen at two of
its approaches to the sun.

{Periodic function} (Math.), a function whose values recur at
fixed intervals as the variable uniformly increases. The
trigonomertic functions, as sin(x), tan(x), etc., are
periodic functions. Exponential functions are also
periodic, having an imaginary period, and the elliptic
functions have not only a real but an imaginary period,
and are hence called doubly periodic.

{Periodic law} (Chem.), the generalization that the
properties of the chemical elements are periodic functions
of their atomic weights. "In other words, if the elements
are grouped in the order of their atomic weights, it will
be found that nearly the same properties recur
periodically throughout the entire series." The following
tabular arrangement of the atomic weights shows the
regular recurrence of groups (under I., II., III., IV.,
etc.), each consisting of members of the same natural
family. The gaps in the table indicate the probable
existence of unknown elements.

{Periodic table}, {Periodic table of the elements} (Chem.), A
tabular arrangement of the chemical elements, illustrating
the {periodic law}, described above.
[1913 Webster]

Note: Note: A modern version of the periodic table can be
found at: http://pearl1.lanl.gov/periodic/default.htm
[PJC] TABLE OF THE PERIODIC LAW OF THE CHEMICAL
ELEMENTS (The vertical columns contain the periodic
groups) Series1[ 2[ 3[ 4[ 5[ 6[ 7[ 8[ 9[ 10[ 11[ 12[
--------------------------------------------------------------
|I. II. III. IV. V. VI. VII. VIII. | RH4 RH3 RH3 RH
|R2O RO R3O3 RO2 R2O5 RO3 R2O7 RO4
--------------------------------------------------------------
H
1
Li
7
Na
23
K
39
(Cu)
63
Rb
85.2
(Ag)
(108)
Cs
133
(-)
(-)
(Au)
(197)

---------------------------------------------------------------
[1913 Webster]

Note: A similar relation had been enunciated in a crude way
by Newlands; but the law in its effective form was
developed and elaborated by Mendelejeff, whence it is
sometimes called {Mendelejeff's law}. Important
extensions of it were also made by L. Meyer. By this
means Mendelejeff predicted with remarkable accuracy
the hypothetical elements ekaboron, ekaluminium, and
ekasilicon, afterwards discovered and named
respectively scandium, gallium, and germanium.
[1913 Webster]

{Periodic star} (Astron.), a variable star whose changes of
brightness recur at fixed periods.

{Periodic time of a heavenly body} (Astron.), the time of a
complete revolution of the body about the sun, or of a
satellite about its primary.
[1913 Webster]