66
u
PERIODICITY AND PREDICTIONS OF PROPERTIES
In this experiment you will make some graphs of periodic properties against
atomic number in order to discover the patterns the properties follow. you will
then use those patterns to predict some properties of elements. In the tast part
of the experiment you will be given a blank periodic table and asked to .rrig,
elements to their proper positions in the table on the basis of their characterisic
properties.
PRELIMINARY STUDY
I
.
2.
Review Sections 7 .3,7 .4, and 7.5 in the text.
Define ionization energy, atomic radius, and metallic character, How do these
properties vary as one goes down a Group in the periodic table? Across
a
period?
PROCEDURE
y',
Usns the data in Table l3-1, plot the atomic radius of each elementonthe
y-axis against its atomic number on the x-axis. Make the x-axis
on the long
side of the paper and choose the scales so that all the data.will fit on the
sheet. Connect each two consecutive points with a straight line. kbel
each
peak with the svmbor of the element.
eni////cl/
ut|
,
//yi/yl/t.
TABLE 13-1 Atomic Radii of the Elements in nm (10{m}
ATOMIC
ELEMENT NUMBER
H
He
Li
Be
B
c
N
o
F
Ne
Itttc
Ms
AI
Si
P
S
ct
Ar
ATOMIC
RADIUS
ELEMENT
1
2
3
4
s
6
7
8
I
10
0.088
0.077
0.070
0.066
0.064
0.070
I
U.166
eu
0.143
Ga
Ge
I
0.037.
K
0.0s0
0.152
Ca
Sc
0.1 11
Ti
12
13
14
15
16
17
18
V
LT
Mn
Fe
Co
Ni
Zn
A.117
0.1 10
0.104
0.099
0.094
As
Se
Br
Kr
ATOMIC
NUMBER
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
ATOMIC
RADIUS
A.231
0.197
0.160
0.146
0.131
0.125
0.129
0.125
0.124
0.128
0.133
0.122
0j22
0.121
0J17
0.114
0.109
fr. using the data in Table l3-2, plot the melting points of the Group
,
1 elements. PIot temperature on the y-axis and atomic number on the x-axis. The
PERIODICITY AND PREDICTIONS OF
PROPERTIES
67
atomic number scale should extend to francium (atornic number 87). Draw
smooth curve through the data points. It will not be a straight line.
TABLE
13-2
ELEMENT
AT. NO.
MELTING POINT ('C}
a
Melting Points of the Group 1 Elements
Li
Na
K
Rb
3
11
t9
37
186
98
64
39
Cs
55
Fr
87
fr' ,'rrin
the blanks in the periodic table provided you by your teacher with the
letter symbol for each of the mystery elements whose properties are described.
The idea is to identify the mystery element and to put its symbol in the
proper place in the blank table. In doing this part of the experiment you may
use the periodic table in your text and any information in the text. You may
find the information in Chapter 7 to be particularly helpful.
(a) A, B, C, and D belong to a family, the members of which are all gases.
A is commonly used in advertising signs. B was hnt discovered on the
sun and is used in weather balloons. C was used to make the first compounds of an element of this eroup. D is the family member which is
present in the largest amount in air.
(b) E and F are members of a family containing both gaseous and sotid
elements. E forms a diatomic molecule and is the major constituent of
the atmosphere. Flement F is a dangerous poison and a metalloid.
(c) G, H, and I belong to a family of very active metals, all of which react
with chlorine to produce salts with the general formula XCl. G is a
member of the first period to contain 18 elements. H has the hi8hest
ionization energy of the family and I has the lowest.
(d) J, K, and L belong to the same family and all are metals. A compound of
J is a major component of bones and teeth. K is commonly used in flash
bulbs for producing light. L is a radioactive element discovered by Marie
' Curie.
(e) M is a gas and has some properties Simiiar to the elements in both Croup
I and Group 7. It is a unique element in this respect.
(O N, O, and P commonly form - I ions when they combine with metals.
N is a liquid and O is a non-radioactive solid. P is the most chemically
reactive of all the non-metals.
fo)
O
R
frmiliec hrrt in the crme fvr.vs.
nerind f)
ic sa
_-t S cnd T ere in differpnf
\P/
<t
Y.o
gas used for water purihcation. R is a yellow non-metallic solid. S is a
metalloid used in transistors. T is a metal of low density used in aircraft
construction.
(h) U, V, W, and X are all transition elements. U is an excellent conductor
of heat and electricity and is commonly used in wiring and cookware.
V is the only inetal that is a liquid at room temperature. W is the metal
which is produced in the largest quantity. Although once used in coins,
X is now used mostly in expensive jewelry.
(i) Y is an actinide fuet used in nuclear reactors. Z is the actinide named
for the creator of the Periodic Table.
I
PERIODICITY AND PREDICTIONS OF PNOPERTIES
68
CALCU LATIONS AND OU ESTIONS
are present in the eanh of atomic radius
l. (a) Describ€ any regrrlaritiel-thal
which etenients occupy the peaks in the cycles?
ver?us atonrlc
(b)
ni,Inu"r.
Are the periods, or cycles, of the same le-ngth?
Fe blank intentionally'
In Table f j-f *t feft tfre atomic radii of Mg and
like to have you predict
The values are actualty known, but we would
on the 8raph' Note lhat
them on the basis of the pattern of properties
thepartofthecyclcfromli(3)tog(5)isrepeatedinthepartofthe
then, that the radius
Z.
cycle from Ni til) to Al (13i. we would expect,
patte,rn observed
of Mg world hlve a value that would maintain ofthe-the Mg atom'
predict.tlrg qdiPs
between H"na B. On that basi3,
(c) As Part of ttr"
gv rrr"-i"g that the Fe (26) atom would
first series of transition mdtals.
atomic number, predict the
maintain the pattem set by atoms near it in
radius of the Fe atorn'
of Mg and Fe on the biriis of radii of ehments
(a) In I we -ffidii
in the periodic tablc'
which lie to the left and rieht of those two elernenb
Thismethodforpredictionismostsuccessfulwhenthcelementsin
questionliewithinacycleandnotatanend.Ifwcattempttopredict
theradiusofanelementattheendofacycle,suchasNa,fromtheradii
wc arc
of elements to the left and right of Na in the_ periodic tablc,
doomedtofailure.Insuch.,""'itisusefultoplotthepropertiesofthe
In the graph made-in Proelements in a Group against atomic number.
points of the Grorp I
cedure 2 we did this when we plotted the melting
elements.Commentonthecrrrveobtained.Isitofaformyouwould
expect for elements within a GrouP?
J,"r""a in Proc"dure-2 can
(b)
b "1ea t9 nreif :}:-T:IT:
Fr (87), which are the other two elements in
ffi;;;
ffi;;ii,-(sit;dneed to extend, or extrapollt"'1"
t-":,11":".T,:
Group l. Here we
":it^
elements in
liehter
the
bv
tn" t'"ni establistred
il#'8;;;ttffie
tlre
pr-edict
qelting.poinS_
gv
extrapolation,
... +^ ^+^6:^
."fi;this
the Group.
Cs and Ft. Ag6in,
Perhaps the
;ourd;f
- ^t,L-
^t
o_f
our values win inose@effi-fffterature'
$rcti information is the
and-Physics.
3.
3, predict the formulas for
using the periodii table prepared in hocedure
compoundsofthefollowingelements:(Usethemysterylette$intheformu.
las.)
(a)
(b)
M. and P
T and Q
(c) EandM
(d) I and R
(e) AandG
(O
JandN
Inpredictingtheformulasyoumayfindthefollowingformulasofknown
substances to be useful:
t,
*i
PHr
HCI
AlBr3
NaI
BaCl,
LizO
fEfRK//lF p TlrE Hnpil 0f ///v/z?r/0/y E/vaF/ r4'fas f7vfi/c ////il6E2) lEtCp/8E 7,/E ffC{/Uilir$ tv rTrE ^
PaTE, ?R//0/(-
H/fH. /5 77E irdzpry
/
lzuary."
a.
tt:
o
o
{
l-
Ft: