Illustrated Glossary of Organic Chemistry
![](period01.png)
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H
2.1
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Li
1.0
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Be
1.5
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B
2.0
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C
2.5
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N
3.0
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O
3.5
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F
4.0
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Na
0.9
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Mg
1.2
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Al
1.5
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Si
1.8
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P
2.1
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S
2.5
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Cl
3.0
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K
0.8
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Ca
1.0
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Sc
1.3
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Ti
1.5
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V
1.6
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Cr
1.6
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Mn
1.5
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Fe
1.8
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Co
1.8
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Ni
1.8
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Cu
1.9
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Zn
1.6
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Ga
1.6
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Ge
1.8
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As
2.0
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Se
2.4
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Br
2.8
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Rb
0.8
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Sr
1.0
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Y
1.2
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Zr
1.4
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Nb
1.6
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Mo
1.8
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Tc
1.9
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Ru
2.2
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Rh
2.2
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Pd
2.2
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Ag
1.9
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Cd
1.7
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In
1.7
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Sn
1.8
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Sb
1.9
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Te
2.1
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I
2.5
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Cs
0.7
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Ba
0.9
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La-Lu
1.1-1.2
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Hf
1.3
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Ta
1.5
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W
1.7
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Re
1.9
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Os
2.2
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Ir
2.2
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Pt
2.2
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Au
2.4
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Hg
1.9
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Tl
1.8
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Pb
1.8
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Bi
1.9
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Po
2.0
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At
2.2
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Fr
0.7
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Ra
0.9
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Ac-No
1.1-1.7
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![](period02.png)
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As one moves from left to right
within a period, atomic number (the total number of electrons)
increases. For example in the second period, lithium (column 1)
has three electrons, beryllium (column 2) has four, and neon
(column 18) has eight.