Question

Aman was discussing the structure of atom with his classmates. During the discussion, he learnt that an element X has a mass number of 35 and contains 18 neutrons. Based on this information, answer the following questions:

1. How many electrons and protons does element X have?
2. What is its atomic number?
3. Identify the element X.
4. Write its electronic configuration.
5. How many valence electrons does it have?
6. What will be the mass number if two neutrons are added to its nucleus?
7. What will be the relation of X with the new atom?

Answer 1

Given:

Mass number (A) = 35 Number of neutrons (n) = 18

Atomic number (Z) = Mass number − Number of neutrons

\[ Z=35-18=17 \]

1. • Number of protons = 17
   • Number of electrons = 17 (for a neutral atom)
2. The atomic number of element X is 17.
3. The element with atomic number 17 is Chlorine (Cl).
4. The electronic configuration of chlorine is 2, 8, 7.
5. Chlorine has 7 valence electrons in its outermost shell.
6. New mass number = 35 + 2 = 37
7. Element X and the new atom are isotopes of chlorine because they have the same atomic number (17) but different mass numbers (35 and 37).