Based on this cell from the periodic table, which statement is true for the element magnesium?

A. A magnesium atom contains 12 protons, and neutral magnesium
atoms contain 24 electrons.
B. A magnesium atom contains 12 protons, and most magnesium
atoms contain 12 neutrons.
C. The atomic number of magnesium is 24.3, and its atomic mass is
12
D. The atomic number of magnesium is 12, and its average atomic
mass is 12

Samir watches a 100-minute movie on his spaceship. maria's spaceshipe flies in the same direction as samir's spaceship but she observes his move to last 125 minutes and his spaceship to be 40 m long. how long does samir observe his own spaceship to be? according to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does marias voyage take according to samir?

If a substance is in the gas phase, which of qualities of the gas will stay constant? a: volume b: mass c: shape d: position of particles

If the textbook weighs 19.6 newtons on venus, what is the strength of gravity on venus?