Thorium

ACTINOID · GROUP None · PERIOD 7

Thorium

232.04

Atomic Data

[Rn] 6d² 7s²

Shell	n	Subshell	Electrons	Cumulative
K	1	1s	2	2
L	2	2s	2	4
L	2	2p	6	10
M	3	3s	2	12
M	3	3p	6	18
M	3	3d	10	28
N	4	4s	2	30
N	4	4p	6	36
N	4	4d	10	46
N	4	4f	14	60
O	5	5s	2	62
O	5	5p	6	68
O	5	5d	10	78
P	6	6s	2	80
P	6	6p	6	86
P	6	6d	2	88
Q	7	7s	2	90
Total			90	90

Thorium is monoisotopic — ²³²Th is its only naturally occurring stable isotope, accounting for 100% of all natural Thorium.

Isotope	Symbol	Protons	Neutrons	Abundance	Stability
Thorium-232	²³²Th	90	142	99.98	Stable

Thorium is present in Earth's crust at approximately 9.6 ppm by mass and at approximately 0.04 ppm by mass throughout the universe.

Thorium

9.6 ppm

Silicon (ref.)

277,000 ppm

Oxygen (ref.)

461,000 ppm

Thorium

0.04 ppm

Helium (ref.)

230,000 ppm

Hydrogen (ref.)

739,000 ppm

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