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:

Even More About the Periodic TablePeriodic Trends

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

Periodic Trends Notes

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

Periodic Trends Notes

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

Periodic Trends Notes