To answer the question correctly, let's break down the information we know about a calcium atom from its symbol, Ca:
1. Atomic Number:
- The symbol "Ca" represents Calcium.
- The atomic number of Calcium is 20. This means that a neutral calcium atom has 20 protons and 20 electrons.
2. Number of Protons:
- Since the atomic number is 20, a calcium atom has 20 protons.
3. Common Isotopes:
- The most common isotope of calcium is Ca-40, meaning it has 20 protons and 20 neutrons (since 40 - 20 = 20).
- Another less common isotope is Ca-44, which has 20 protons and 44 - 20 = 24 neutrons.
Given these details, let's evaluate the options:
A. A calcium atom has 44 neutrons and 20 electrons.
- While this option mentions 20 electrons correctly for a neutral atom, it incorrectly states the common number of neutrons. The more common isotope has 20 neutrons, not 44.
B. A calcium atom has 20 protons and 24 electrons.
- This is incorrect because a neutral calcium atom should have 20 electrons, not 24. The only time it may have 24 electrons is if it were an ion with a -4 charge, which is uncommon for calcium.
C. A calcium atom has 20 protons and 44 neutrons.
- This is incorrect because while it is possible for an isotope of calcium to have 44 neutrons, it would have an atomic mass of approximately 64 (20 protons + 44 neutrons).
D. A calcium atom has 64 protons and 20 neutrons.
- This is incorrect because the atomic number of calcium is 20, which means it cannot have 64 protons.
E. A calcium atom has 20 protons and 24 neutrons.
- This is incorrect for common isotopes since the most common isotope, Ca-40 has 20 neutrons. Less common isotopes have varying numbers of neutrons but 20 protons are consistent in each isotope.
Correct option:
The correct understanding is:
- A calcium atom has 20 protons
- Most common isotope: Ca-40 has 20 neutrons
- A less common isotope: Ca-44 has 44 neutrons
Therefore, none of the options given in the question correctly describe both the number of protons and neutrons in a calcium atom. The closest solution based on the general knowledge of calcium atom structure would be:
- 20 protons and 20 neutrons (common isotope Ca-40)
- Or, in less common cases, 20 protons and 44 neutrons (Ca-44).
However, based on the options explicitly given, none match this description exactly. The option providing most aligned information considering common isotopes would be noting the number of protons more crucially (20). Thus, none of the options especially E fits scientifically standard isotopes in the question set provided. One should adjust set options for correct descriptive Isotopes of Calcium next consideration.
