10. The statement that no two electrons in the same atom can have the 7. Among the following groups
of atoms, which have the same
number of electrons in their
outermost energy level?
A) Na, Mg, Al and Si
B) Ca, K, Al and Ne
C) Mg, Ca, Sr and Ba.
D) H and He

10.the pauli exclusive principle statues that, in an atom

or molecules, no two electrons can have same four electronic quantum numbers.as an orbit can contain a maximum of only two electrons.the two electrons must have opposing spins

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.