When adding or subtracting deelmals, how many digits should the answer contain?

Depends, but in most cases, 2.

It's best to use as many digits as possible to keep it accurate.

Explanation:

This varies between teachers, as most schools go with 2 decimal places.

This is something that depends in your situation.

You technically want as many decimals as possible to keep it as accurate, but most people stick with 2.

I personally do 3, and commonly do 5 sometimes.

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.

c (diamond),

sio2 (quartz)