Chapter 1 School Practice Questions

Question 1

problem 1.39

Answer 1

Two radioactive isotopes of iodine are provided with mass numbers 123 and 131. For each isotope:

Number of protons:
Iodine always has 53 protons (this is its atomic number).

Number of neutrons:

For Iodine-123:
123−53=70 neutrons.
For Iodine-131:
131−53=78 neutrons.
Number of electrons in the neutral atom:
A neutral atom has the same number of electrons as protons. So, each isotope has 53 electrons.

Group number:
Iodine belongs to Group 17 (halogens).

Question 2

1.40 Label each bond as ionic or covalent:

Answer 2

a. NaI: Ionic bond (sodium is a metal, and iodine is a non-metal).
b. BrCl: Covalent bond (both bromine and chlorine are non-metals, and the electronegativity difference is small).
c. HCl: Covalent bond (both are non-metals, but it’s polar covalent due to the electronegativity difference).
d. CH₃NH₂: Covalent bonds (all atoms involved are non-metals, forming covalent bonds).
e. NaOCH₃: Ionic bond (sodium forms an ionic bond with the OCH₃ group).