francium
Rarest natural element
Francium is a radioactive metallic element, atomic number 87, the heaviest of the alkali metals.
It is extremely rare and unstable—the most unstable of the first 101 elements—with its longest-lived isotope having a half-life of only about 22 minutes.
Francium occurs naturally in trace amounts from the decay of actinium but has no practical applications.
Eleventh element, highly reactive
- potassiumNineteenth element, symbol K
- lithiumLightest solid element
- rubidiumAlkali metal, atomic thirty-seven
- cesiumAlkali metal, number fifty-five
electropositive · reactivity · hydroxide · ionization · flame test · oxidation · alkaline
Gradual organic breakdown
- half-lifePeriod for fifty-percent reduction
- alphaFirst Greek letter
- betaGreek alphabet's second letter
- gammaGreek alphabet's third
radiation · unstable · isotopes · transmutation · ionizing · radionuclide · emission · activity
Systematic display of elements
- atomic numberProton quantity per nucleus
- chemistryStudy of substances' interactions
- protonsPositive nuclear particles
- neutronsUncharged subatomic particles
electrons · nucleus · atomic mass · valence · orbitals · subatomic · quantum · discovered
In short supply
- ephemeralLasting very briefly
- transientTemporary, soon departing
- elusiveHard to find
- traceMinute remnant or pursue
fleeting · short-lived · unstable · minuscule · undetectable
sodium
Eleventh element, highly reactive
- potassiumNineteenth element, symbol K
- lithiumLightest solid element
- rubidiumAlkali metal, atomic thirty-seven
cesium · electropositive · reactivity · hydroxide · ionization · flame test · oxidation · alkaline
decay
Gradual organic breakdown
- half-lifePeriod for fifty-percent reduction
- alphaFirst Greek letter
- betaGreek alphabet's second letter
gamma · radiation · unstable · isotopes · transmutation · ionizing · radionuclide · emission · activity · disintegration
periodic table
Systematic display of elements
- atomic numberProton quantity per nucleus
- chemistryStudy of substances' interactions
- protonsPositive nuclear particles
neutrons · electrons · nucleus · atomic mass · valence · orbitals · subatomic · quantum · discovered · 1939
scarce
In short supply
trace · fleeting · short-lived · unstable · minuscule · undetectable
- elementsoxygen, hydrogen, carbon, helium, nitrogen
- metalsaluminum, steel, copper, iron, gold
- Alkali Metalslithium, sodium, potassium, rubidium, cesium
- main group elementshydrogen, helium, lithium, beryllium, boron
- Radioactive Elementsuranium, plutonium, radium, radon, thorium
- reactive metalssodium, potassium, lithium, cesium, rubidium
- San FranciscoNorthern California metropolis
- San Francisco BayNorthern California coastal inlet
- San Francisco Bay AreaNorthern California coastal metropolitan region
- San Francisco GiantsBay Area baseball franchise
- San Francisco earthquakeMajor California temblor event
- San FranciscanResident of northern California metropolis