Plutonium-196 has an atomic number of 78. It has neutrons.

118 neutrons

Explanation:

There are three subatomic particles in an atom namely: electron, neutron and proton. The mass number of an atom is calculated by adding the proton no. (atomic mass) + neutron no.

That is;

Mass no. = proton no. + neutron no.

This means that to obtain the neutron no. in the atom of an element, we subtract the no of protons or atomic mass from the mass number.

According to this question, Plutonium-196 is said to have an atomic number of 78. The mass no. is 196, hence, the number of neutrons is:

196 - 78

= 118 neutrons.

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.