To determine the correct answer by analyzing the symbol \( \ce{^{44}_{20}Ca} \), we need to understand what the atomic number and the mass number represent.
1. Atomic Number (20):
- The atomic number is located at the bottom of the symbol. It tells us the number of protons in the nucleus of the atom.
- Therefore, in this calcium atom, there are 20 protons.
2. Mass Number (44):
- The mass number is located at the top of the symbol. This represents the total number of protons and neutrons in the nucleus.
- For this calcium atom, the mass number is 44.
3. Number of Neutrons:
- The number of neutrons can be calculated by subtracting the atomic number from the mass number.
- Therefore, the number of neutrons is \( 44 - 20 = 24 \).
4. Number of Electrons:
- In a neutral atom, the number of electrons equals the number of protons.
- Therefore, this calcium atom has 20 electrons.
Based on this information, among the choices provided:
A. A calcium atom has 44 neutrons and 20 electrons. (Incorrect - It has 24 neutrons, not 44)
B. A calcium atom has 20 protons and 24 electrons. (Incorrect - It has 20 electrons, not 24)
C. A calcium atom has 64 protons and 20 neutrons. (Incorrect - It has 20 protons and 24 neutrons)
D. A calcium atom has 20 protons and 24 neutrons. (Correct - Matches our calculations)
E. A calcium atom has 20 protons and 44 neutrons. (Incorrect - It has 24 neutrons, not 44)
Thus, the correct answer is:
D. A calcium atom has 20 protons and 24 neutrons.
