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atoms

circles comparing size of a cesium and a hydrogen atom

The largest and smallest atoms.

What does it mean to measure the “size” of an atom?

An atom is not like a billiard ball. We know it has a posoitively charged center (the nucleus), which is surounded by mving electrosn. n atom is not like a minature solre sysem either, though it is sometimes helpful to think of it that wat.An atoms electrons don't travil in regualr orbits. They are cfound in clouds. Distance beteen teh central charge and the outermost electron.

get them to form a crystl. The atoms in a crystel are arannged in a regular pattern. I one shines x-rays through the crystel onto a sensor, such as a sheet of photographic film, a pattern of spots . From this pattern scientist are able to distance ebetween the atoms and from thst,

Element	Symbol	Atomic number	Atomic radius in nanometers
hydrogen	H	1	0.037
helium	He	2	0.05
lithium	Li	3	0.152
beryllium	Be	4	0.111
boron	B	5	0.088
carbon	C	6	0.077
nitrogen	N	7	0.070
oxygen	O	8	0.066
fluorine	F	9	0.064
neon	Ne	10	0.070
sodium	Na	11	0.186
magnesium	Mg	12	0.160
aluminum	Al	13	0.143
silicon	Si	14	0.117
phosphorus	P	15	0.110
sulfur	S	16	0.104
chlorine	Cl	17	0.099
argon	Ar	18	0.094
potassium	K	19	0.231
calcium	Ca	20	0.197
scandium	Sc	21	0.162
titanium	Ti	22	0.146
vanadium	V	23	0.134
chromium	Cr	24	0.127
manganese	Mn	25	0.126
iron	Fe	26	0.126
cobalt	Co	27	0.125
nickel	Ni	28	0.124
copper	Cu	29	0.128
zinc	Zn	30	0.138
gallium	Ga	31	0.122
germanium	Ge	32	0.122
arsenic	As	33	0.121
selenium	Se	34	0.117
bromine	Br	35	0.114
krypton	Kr	36	0.109
rubidium	Rb	37	0.244
strontium	St	38	0.215
yittrium	Y	39	0.180
zirconium	Zr	40	0.160
niobium	Nb	41	0.146
molybdenum	Mo	42	0.139
technetium	Tc	43	0.136
ruthenium	Ru	44	0.134
rhodium	Rh	45	0.134
palladium	Pd	46	0.137
silver	Ag	47	0.144
cadmium	Cd	48	0.154
indium	In	49	0.162
tin	Sn	50	0.140
antimony	Sb	51	0.141
tellurium	Te	52	0.137
iodine	I	53	0.133
xenon	Xe	54	0.130
cesium	Cs	55	0.262
barium	Ba	56	0.217
lanthanum	La	57	0.187
cerium	Ce	58	0.182
praseodymium	Pr	59	0.182
neodymium	Nd	60	0.182
promethium	Pm	61
samarium	Sm	62
europium	Eu	63	0.204
gadolinium	Gd	64	0.179
terbium	Tb	65	0.177
dysprosium	Dy	66	0.177
holmium	Ho	67	0.176
erbium	Er	68	0.175
thulium	Tm	69	0.174
ytterbium	Yb	70	0.193
lutetium	Lu	71	0.174
hafnium	Hf	72	0.158
tantalum	Ta	73	0.146
tungsten	W	74	0.139
rhenium	Re	75	0.137
osmium	Os	76	0.135
iridium	Ir	77	0.136
platinum	Pt	78	0.138
gold	Au	79	0.144
mercury	Hg	80	0.157
thallium	Tl	81	0.171
lead	Pb	82	0.175
bismuth	Bi	83	0.146
polonium	Po	84	0.15
astatine	At	85	0.14
radon	Rn	86	0.14
francium	Fr	87	0.27
radium	Ra	88	0.220
actinium	Ac	89	0.1065¹
thorium	Th	90	0.180
protactinium	Pa	91
uranium	U	92	0.14
neptunium	Np	93
plutonium	Pu	94
americium	Am	95
curium	Cm	96
berkelium	Bk	97
californium	Cf	98
einsteinium	Es	99
fermium	Fm	100
mendelevium	Md	101
nobelium	No	102
lawrencium	Lr	103
rutherfordium	Rf	104
dubnium	Db	105
seaborgium	Sg	106
bohrium	Bh	107
hassium	Hs	108
meitnerium	Mt	109
darmstadtium	Ds	110
roentgenium	Rg	111
copernicium	Cn	112
nihonium	Nh	113
flerovium	Fl	114
moscovium	Mc	115
livermorium	Lv	116
tennessine	Ts	117
oganesson	Og	118

sources

1. Gauthier J.-P.Deblonde, Mavrik Zavarin, and Annie B. Kersting.
The coordination properties and ionic radius of actinium: A 120-year-old enigma.
Coordination Chemistry Reviews, vol. 446, 1 November 2021, 214130
doi.org/10.1016/j.ccr.2021.214130

2. R. D. Shannon.
Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides.
Acta Crystallographica, Section A. 32 (5) pages 751–767, (1976).
doi.org/10.1107/S0567739476001551.

resources

www.rsc.org/periodic-table/

Both the content and design of this site created by the Royal Society of Chemistry (UK) are truly exceptional. Be sure to check out the videos.

The current version is at least the second. The animations in the original were huge for the time (hydrogen was about 12 megabytes), so downloading and saving them was a wise use of bandwidth—or one could buy a CD for $37 (20 pounds). Now the videos stream and the CD seems no longer on offer. We wish we had saved one of the first edition videos, for the sake of comparison.

Philip Ball.
The Ingredients. A Guided Tour of the Elements.
Oxford University Press, 2003.

John Emsley.
Nature's Building Blocks. An A-Z Guide to the Elements.
Oxford University Press, 2002.

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