Question

Sodium atoms and sodium ions:
(A) are chemically similar
(B) both react vigorously with water
(C) have same number of electrons
(D) have same number of protons

Answer 1

Hint: Sodium is an atom with an atomic mass of 23 and having an atomic number of 11. With the help of the above concept, we will solve the above question.

Complete answer:

First, we will see for the sodium atom:
The sodium atom has an atomic mass of 23 and the atomic number of sodium is 11. As we know:
- The atomic mass of an atom = the number of protons in an atom.
- Hence, the number of protons in a sodium atom is 11. We also know that the sodium atom is a neutral atom i.e. the sodium atom does not have any charge over it, which means that the number of electrons and protons in an atom is equal. Therefore, the sum of protons and neutrons is equal to the atomic mass of that atom.
${\text{atomic mass of an atom = number of protons + number of neutrons}}$
23 = 11 + {\text{ number of neutrons in sodium atom}} \\\ {\text{number of neutrons in sodium atom = 12}} \\\
Therefore, we know that:
- The number of neutrons in sodium atom = 12
- The number of electrons in sodium atom = 11
- The number of protons in sodium atom = 11
Now, we will see for the sodium ion:
- The atomic mass of sodium atom is =23
- The number of protons is = 11
As, the sodium ion is not a neutral ion so the number of electrons is = 10
So, Option (a),(b),(c) are not correct as they have different numbers of electrons hence they have different chemical properties as only sodium atom reacts only with water while sodium atom does not react with water.
So, we see that only option number (d) is correct.

Note:The sum of the protons and neutrons is equal to the atomic mass of the atom. While the number of electrons is equal to the number of protons for a neutral atom. For a positive ion the charge of the ion determines the number of electrons that are less than the number of protons.