What element has the greatest atomic radius?

Answer 1

The element cesium, at the left of row 6, is often cited as having the largest radius.

However, francium in row 7 may be larger. There is almost no francium on Earth,

as its half-life is 21.8 minutes.

*The elements of the lower left hand side of the Periodic Table have the largest atomic radius. The upper right has the smallest.

Answer 2

Cesium (Cs), tucked in the lower left hand corner of the table, has the largest known atoms. The atomic radius of Cs is given variously as 273.1 pm [1], 265 pm [2], 265.5 pm [3] or 260 pm [4]. Rubidium also has large atoms, but its atomic radius is almost 30 pm less than cesium's.

Why are cesium atoms so big? Cesium has a large valence shell and a relatively low effective nuclear charge. The valence shell (the outer 'peel' of the atom) is largest in atoms at the bottom of the periodic table. A low nuclear charge means that electrons can wander further, on average, from the nucleus. Nuclear charge increases going left to right across table rows, so the largest atoms should be found on the left edge of the table.

Does having such large atoms make any difference in cesium's properties? Yes. Cesium is one of the most reactive elements known, partially because its atoms are so large. Cesium's lone valence electron is so far away from the nucleus on average that it is very easily removed. The electron is taken from cesium by other substances in violent chemical reactions. Cesium bursts into flames on contact with oxygen in air. Water and even ice reacts more violently with cesium than any of the other common metals:

2 Cs(s) + 2 H2O() 2 CsOH(aq) + H2(g)

Why aren't francium atoms the biggest? The usual periodic trend for atomic size places larger atoms at the left of a row and towards the bottom of a column on the periodic table. It's no surprise that cesium is large. But shouldn't francium, in the next period with an even larger valence shell, be even larger?

The answer is "possibly, but we just don't know yet." Francium isn't easy to study. It's the least stable of the first 103 elements; the most stable Fr isotope has a half-life of just 22 minutes [5].

Answer 3

The current largest atomic radius known is that of Caesium (Cesium in USA) with a empirically measured atomic radius of about 298 picometers.

Answer 4

The largest atomic radius is for caesium - 260 pm.

Answer 5

Francium has an atomic radius of 348 pm (Royal Society of Chemistry).

Answer 6

Element Cesium has the largest atomic radius.It is represented by symbol Cs.The atomic radius of Cs is approximately 272 pm.

Answer 7

Francium (Fr)

Answer 8

lower left hand corner

Answer 9

Francium