Question

name the compound CH3=CH2-CH3=CH2

Answer 1

this compound doesn't exist because
valency of Carbon is four
i.e. it can accommodate only four bounds

But in chain first carbon have 5 bounds ( 3 with Hydrogen and double sound with carbon)

second carbon have 5 bounds

third carbon have 6 bounds

so it is wrong

May be the right chain is

CH3-CH2-CH2-CH3 ( Butane)
or
CH2=CH-CH2-CH3 ( Butene)
or
H-C=_C-CH2-CH4 (Butyne)
[=_ represent triple bound ]

Answer 2

Answer:

CH3=CH2-CH3=CH2 is not possible .In this carbon is showing a valency more than 4. It can't exist.

But if you still want it's name it will be  But 1,3- diene.

But then your comment says that there are  in the questions 4 carbon atoms and 10 hydrogen atoms.

In that case the name will be Butane ( C4H10).