When a potassium atom forms an ion, it loses one electron. what is the electrical charge of the potassium ion?
a. -1
b. -2
c. +2
d. +1

If a potassium atom loses one electron than it becomes a +1 charge, because the electrons are negative and the nucleus is positive (the positive comes from the protons). The protons and electrons balance out so it has a neutral charge, but if the atom loses an electrons it has a positive charge, but if the atom gains an electron than it becomes negative. the charge (+/- and the number) of the atom depends on how many electron the atom gains/loses. 
the answer is (D.) +1

I hope this helps.

Initial velocity,  u = 4.9 m/sfinal velocity = v m/sinitial height,  h₁ =  245 m    final height, h₂ = 0a = -9.8  m/s²time taken = t secondss = ut + 0.5at²⇒  (h₂-h₁) = ut + 0.5at²⇒  0-245 = 4.9t + 0.5×(-9.8)×t²⇒ -245 = 4.9t - 4.9t²⇒ 4.9t² -4.9t -245 =0solving it, we get   t = 7.59sv  = u +  at = 4.9 -9.8×7.59 = 4.9 - 74.38 = -69.48 m/svelocity is  69.48 m/s downward