The Nebular Theory explains the formation of: A). only planets

B). galaxies

C). the Universe

D). a Star and orbiting planets

The Answer is D: A star and orbiting planets

Explanation:

Not to be confused with the Big Bang theroy (which "explains" the origin of the universe)  The Neublar Theory explains the  formation of the solar system, which is bascially A star and orbiting planets.

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the answer is learned

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.