Sodium (Na) has an atomic mass of 23 and an atomic number of 11.
a. How many protons/neutrons/electrons does it have?
b. Draw the electron shells.
c. How many electrons will it gain or lose?
d. What is the final charge on Sodium?
The correct answer and explanation is:
Correct Answers:
a. Sodium (Na) has:
- 11 protons
- 11 electrons
- 12 neutrons (Atomic mass 23 – Atomic number 11 = 12)
b. Electron shell configuration:
- 1st shell: 2 electrons
- 2nd shell: 8 electrons
- 3rd shell: 1 electron
c. Sodium will lose 1 electron to achieve a stable electron configuration.
d. The final charge on sodium will be +1.
Explanation (300 words):
Sodium (Na) is a chemical element found in group 1 of the periodic table, meaning it is an alkali metal. It has an atomic number of 11, which indicates that it has 11 protons in its nucleus. Because atoms are neutral by default, a neutral sodium atom also contains 11 electrons to balance the 11 protons. The atomic mass of sodium is 23. The number of neutrons in an atom can be calculated by subtracting the atomic number from the atomic mass: 23 – 11 = 12. So sodium has 12 neutrons.
The electrons in an atom are arranged in shells around the nucleus. The first shell can hold up to 2 electrons, the second shell can hold up to 8 electrons, and the third shell begins to fill next. For sodium, the 11 electrons are arranged as 2 in the first shell, 8 in the second, and 1 in the third shell.
Sodium tends to react in ways that lead to a full outer electron shell. Since it only has one electron in its outermost shell, it is energetically favorable for sodium to lose that one electron. Losing this electron leaves sodium with a full second shell, which is stable. When an atom loses an electron, it has more protons than electrons and becomes positively charged. Therefore, after losing one electron, sodium becomes a positive ion (Na⁺) with a charge of +1.
This behavior of sodium is typical of alkali metals and explains why sodium easily forms ionic compounds like sodium chloride (NaCl) by transferring its outer electron to a more electronegative element such as chlorine.