What is the atomic number of AC

Actinium

Actinium: characteristics

Atomic number:

89

Symbol:

Ac

Name (German / English):

Actinium (official name according to IUPAC)

Group:

Scandium group

IUPAC group:

3 (old nomenclature: Group III B (Ac))

Period:

7

Dimensions (approx):

[227,0277] u (no reliable measured value available)

Discoverer:

Debierne

Discovery year:

1899

Occurrence:

arises through natural radioactive decay processes

Frequency:

6,00 · 10-14 % (percentage by mass of the earth's shell, i.e. the earth's crust / oceans up to 16 km depth)

CAS number [1]:

7440-34-8

Actinium: atomic properties

Atomic radius (empirical):

195 pm

Atomic volume:

22.5 cm3/ mol

Ionization energies:

kJ / moleV
1.499 kJ / mol5.172 eV
2.1170 kJ / mol12.126 eV

Oxidation numbers:

III

Electronegativity (Pauling):

1,1

Electronegativity (Allred / Rochow):

1

Ionic radius:

118 pm

Number nat. Isotopes:

2r

Number of stable isotopes:

0

Number of unstable isotopes:

11

Radioactive isotopes:

isotopeHalf-life
227Ac21.8a (i.e. years, from lt. annus)

(The list contains only the most important isotope with a known half-life.)

Electron configuration:

[Rn] 6d 7s2
OrbitalElectrons
1s2
2s2
2p6
3s2
3p6
3d10
4s2
4p6
4d10
4f14
5s2
5p6
5d10
5f0
6s2
6p6
6d1
7s2
7p0

Shell model:

  • 2 electrons in the outermost occupied shell
  • 9 electrons in the second to last occupied shell
  • 18 electrons in the occupied shell below

Actinium: substance properties

Melting point:

1320 K (~ 1046.85 ° C)

Boiling point:

3471 K (~ 3197.85 ° C)

State of aggregation:

fixed (under normal conditions)

Crystal structure:

Cubic area-centered

Metal properties:

Inner transition metal (actinide)

Thermal conductivity:

12 W / m / K

Specific heat capacity:

0.12 J / gK

Electric conductivity:

106 · 106 S / m

Specific density:

10.07 g / cm3
(under normal conditions)


 
Remarks:
  1. The "CAS Registry Number" is that of the element Actinium from Chemical Abstracts Service Assigned key number, which makes it easier to find specialist articles about this element in all publications and databases structured according to the CAS system.
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