Question

niels bohr (early 1900s):
niels bohr was a danish physicist. he proposed a model of the atom that is similar to the model of the solar system. the electrons go around the nucleus like planets orbit around the sun. all electrons have their energy levels - a certain distance from the nucleus. each energy level can hold a certain number of electrons. level 1 can hold 2 electrons, level 2 - 8 electrons, level 3 - 18 electrons, and level 4 - 32 electrons. the energy of electrons goes up from level 1 to other levels. when electrons release (lose) energy they go down a level. when electrons absorb (gain) energy, they go to a higher level.

1. why could bohrs model be called a planetary model of the atom?
2. how do electrons in the same atom differ?
3. how many electrons can the fourth energy level hold?
4. would an electron have to absorb or release energy to jump from the second energy level to the third energy level?
5. for an electron to fall from the third energy level to the second energy level, it must energy.

Explanation:

1. The text clearly states that in Bohr's model, electrons' motion around the nucleus is analogous to planets orbiting the sun, which is the reason for the "planetary" name.
2. The passage mentions that all electrons have their energy levels (a certain distance from the nucleus), so this is how electrons in the same atom differ.
3. The text directly gives that level 4 (the fourth energy level) can hold 32 electrons.
4. Since when electrons go to a higher level, they absorb (gain) energy, and the third level is higher than the second, an electron jumping from the second to the third must absorb energy.
5. As per the text, when electrons go down a level, they release (lose) energy. Here, going from the third (higher) to the second (lower) level means releasing energy.

Answer:

1. Because electrons go around the nucleus like planets orbit around the sun.
2. They have different energy levels (different distances from the nucleus).
3. 32 electrons.
4. Absorb energy.
5. Release.