Because they have the same number of electrons in the outer shell, they have the same reactivity (they all want to lose/gain a certain amount of electrons to have a full shell of 8), so they have the similar melting, boiling points etc because they all undergo very similar reactions to certain factors so have similar outcomes
True, bc each element emits lights that have an unique wavelength and frequency
Heterogeneous, which means that they are not evenly combined.
1 3/4 Ounces or 1.75 Ounces!
Basically 21/12 = 1.75!
(Mark me as the brainliest if this helps!)