Question

how many valence electrons are in the trimethylammonium ion $(ch_{3})_{3}nh^{+}$?

Explanation:

Step1: Count valence electrons for each atom

Carbon ($C$) has 4 valence electrons. There are 3 carbon atoms in $\ce{(CH3)3NH+}$, so $3\times4 = 12$ valence electrons from $C$.
Hydrogen ($H$) has 1 valence electron. There are $3\times3 + 1=10$ hydrogen atoms, so $10\times1 = 10$ valence electrons from $H$.
Nitrogen ($N$) has 5 valence electrons. There is 1 nitrogen atom.
Since the ion has a $+1$ charge, we subtract 1 electron (because a positive charge means loss of 1 electron).

Step2: Calculate total valence electrons

Total valence electrons $=(12 + 10+5)-1$
$=26$

Answer:

26