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The Diatomics
They are elements that are found as two atoms bonded to themselves.
They are H2, N2, O2, F2, Cl2, Br2, I2
There are 7 of them and they are located here:
Atomic radius - one-half the distance between the nuclei of two atoms of the same element when the atoms are joined
In general, atomic size increases from top to bottom within a group and decreases from left to right across a period.
Trends in Atomic Size
Cations are always smaller than the atoms from which they form.
Anions are always larger than the atoms from which they form.
Trend in Ionic Size
First ionization energy tends to decrease from top to bottom within a group and increase from left to right across a period.
Trends in Ionization Energy
In general, electronegativity values decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period.
Trends in Electronegativity
The trends that exist among these properties can be explained by variations in atomic structure.
The increase in nuclear charge within groups and across periods explains many trends.
Within groups an increase in shielding (distance from the nucleus) has a significant effect
Summary of Trends
1
2
18
17
16
15
14
13
Atomic size DECREASESIonization energy INCREASESElectronegativity INCREASESNuclear charge INCREASESShielding is constant
Ato
mic
siz
e IN
CR
EA
SE
SIo
niz
ati
on
en
erg
y
DE
CR
EA
SE
SE
lect
ron
eg
ati
vit
y
DE
CR
EA
SE
SN
ucl
ear
charg
e
INC
RE
AS
ES
Sh
ield
ing
IN
CR
EA
SE
SIo
nic
siz
e IN
CR
EA
SE
S
Size of cations decreases Size of anions
decreases