This element is Helium. This is because it has two protons and two neutrons in its nucleus. this makes it have the atomic mass of approximately four atomic mass units. It also has two electrons in the first energy level. . It is therefore a noble gas since this is the only energy level and it obeys the 2n² rule for the filling of energy levels. n in this case is 1 making the maximum number of electrons in the first energy level to be 2.
12
The atomic number is equal to the number of protons in the nucleus
The answer is: distance is 3 km, displacement is 2.24 km.
Distance is total length: 1 km east + 1 km south + 1 km east again = 3 km
Displacement is the hypotenuse of the right triangles which sides are 1 km east and 2 km south. According to the Pythagorean theorem:
a² + b² = c²
1² + 2² = c²
1 + 4 = c²
5 = c²
c = √5
c = 2.24 km
