Francium in the context of Decay chain

The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). Together with hydrogen they constitute group 1, which lies in the s-block of the periodic table. All alkali metals have their outermost electron in an s-orbital: this shared electron configuration results in them having very similar characteristic properties. Indeed, the alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterised homologous behaviour. This family of elements is also known as the lithium family after its leading element.

The alkali metals are all shiny, soft, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge +1. They can all be cut easily with a knife due to their softness, exposing a shiny surface that tarnishes rapidly in air due to oxidation by atmospheric moisture and oxygen (and in the case of lithium, nitrogen). Because of their high reactivity, they must be stored under oil to prevent reaction with air, and are found naturally only in salts and never as the free elements. Caesium, the fifth alkali metal, is the most reactive of all the metals. All the alkali metals react with water, with the heavier alkali metals reacting more vigorously than the lighter ones.

In chemistry, a hydride is formally the anion of hydrogen (H), a hydrogen ion with two electrons. In modern usage, this is typically only used for ionic bonds, but it is sometimes (and has been more frequently in the past) applied to all compounds containing covalently bound H atoms. In this broad and potentially archaic sense, water (H₂O) is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. In covalent compounds, it implies hydrogen is attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed.

Almost all of the elements up to Cf form binary compounds with hydrogen, the exceptions being He, Ne, Ar, Kr, Pm, Rn, Fr, and Ra. Exotic molecules such as positronium hydride have also been made.

A liquid metal is a metal or a metal alloy which is liquid at or near room temperature.

The only stable liquid elemental metal at room temperature is mercury (Hg), which is molten above −38.8 °C (234.3 K, −37.9 °F). Three more stable elemental metals melt just above room temperature: caesium (Cs), which has a melting point of 28.5 °C (83.3 °F); gallium (Ga) (30 °C [86 °F]); and rubidium (Rb) (39 °C [102 °F]). The radioactive metal francium (Fr) is probably liquid close to room temperature as well. Calculations predict that the radioactive metals copernicium (Cn) and flerovium (Fl) should also be liquid at room temperature.

A period 7 element is one of the chemical elements in the seventh row (or period) of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behavior of the elements as their atomic number increases: a new row is begun when chemical behavior begins to repeat, meaning that elements with similar behavior fall into the same vertical columns. The seventh period contains 32 elements, tied for the most with period 6, beginning with francium and ending with oganesson, the heaviest element currently discovered. As a rule, period 7 elements fill their 7s shells first, then their 5f, 6d, and 7p shells in that order, but there are exceptions, such as uranium.