Hello!
The atomic number is determined only by the number of protons in the nucleus of an atom. But, in a neutral atom it also represents the number of electrons in the electron cloud.
Neutrons are only important in the nucleus for helping us find atomic weight, which varies as we move along the perodic table and does not always equal the same amount of it's atomic number. Which is why it would not be a suitable answer for the first blank space. Electrons do not work either as they do not exist inside the nucleus but rather outside the atom.
The second space, since it states is in the electron cloud, we can deduct that electrons would be an appropriate answer there.
If you need anymore help feel free to ask, but I hope this answers your question.
Answer: Potential energy is converted to kinetic energy and back again.
Explanation:At points 1 and 3, the pendulum stops moving, and its mechanical energy is purely potential. At point 2, the pendulum is moving the fastest, and its mechanical energy is purely kinetic. Therefore, as the pendulum moves from point 1 to point 3, its potential energy is first converted to kinetic energy, then back to potential.
Answer is (4) - Pb.
According to the reactivity series of elements
- the elements which are above the hydrogen are more reactive than hydrogen.
- the elements which are below the hydrogen are less reactive than hydrogen.
Among the given choices, only Pb is placed above the hydrogen in the reactivity series and rest are below the hydrogen.
Hence, Pb is more active than hydrogen.
