Question

Only answer 28 ( I added this parentheses so that the thing would accept my question)

Answer 1

(a). Number of protons in a chlorine atom = 17

(b). Atomic number of sodium = 11

Explanation:

Let the number of protons in a sodium atom = x

Then, the number of protons in a chlorine atom = x + 6

Now, it is given that the atomic number of an element is equal to the number of protons per atom.

So, atomic number of sodium (Na) = x

Atomic number of chlorine (Cl) = x + 6

It is given that the atomic number of chlorine is 5 less than twice the atomic number of sodium.

∴ atomic number of chlorine (Cl) = 2 × atomic number of sodium (Na) - 5

⇒ x + 6 = 2x - 5

⇒ x - 2x = -5 - 6

⇒ -x = -11

Cancelling the minus sign from both sides, we get

x = 11

(a). Number of protons in a chlorine atom = x + 6

= 11 + 6 (∵ x = 11)

= 17

(b). Atomic number of sodium = x = 11