Which of these statements is not true?
a. atoms of the same elements can have different masses.
b. the nucleus of an atom has a positive charge.
c. atoms of isotopes of an element have different numbers of protons.
d. atoms are mostly empty space.

The boy of mass 30 kg is at r1= 2 meters from the fulcrum. of the girl is 45 kg, at what r2 must she sit so that they are balanced ?

Which transition by an electron will release the greatest amount of energy? oa ob oc od

Marcella is a four-year-old girl who is a victim of emotional child abuse. based on the child and family services improvement and innovation act of 2011, which action should the government take for marcella? a. the state should arrest marcella’s abuser. b. the state should find a home for marcella as soon as possible. c. the state should enforce stricter laws in the area where marcella resides. d. the state should provide medical assistance to marcella.