Matter that has a definite volume but no definite shape is a

liquid state

Explanation:

There are three states of matter:

 Gaseous state : It is a state in which the particles are loosely arranged and have a lot of space between them. This state has indefinite volume as well as a definite shape.

Liquid state : It is a state in which the particles are present in random and irregular pattern. The particles are closely arranged but they can move from one place to another. This state has a definite volume but does not have a fixed shape.

Solid state : It is a state in which the particles are closely packed and does not have any space between them. This state has a definite shape and a definite volume.

Thus liquid state has has a definite volume but no definite shape.

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.