NCERT Solutions for Class 9 Science Chapter 3
Atoms And Molecules
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Intext Questions
Page No-39
Questions No-14
(i) H₂S molecule and
(ii) PO₄³⁻ ion?
How many atoms are present in a (i) H₂S molecule and (ii) PO₄³⁻ ion?
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(i) In an H₂S molecule, three atoms are present; two of hydrogen and one of sulphur.
(ii) In a PO₄₃- ion, five atoms are present; one of phosphorus and four of oxygen.
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(i) H₂S molecule (Hydrogen sulfide):
– Hydrogen sulfide (H₂S) comprises 2 atoms of hydrogen (H₂) and 1 atom of sulfur (S) per molecule.
– Thus, within one molecule of hydrogen sulfide, there are a total of 3 atoms: 2 hydrogen atoms and 1 sulfur atom.
(ii) PO₄³⁻ ion (Phosphate ion):
– The phosphate ion (PO₄³⁻) consists of 1 atom of phosphorus (P) and 4 atoms of oxygen (O₄).
– The ion carries a 3- charge, indicating the addition of three electrons, but not involving extra physical atoms.
– Consequently, in one phosphate ion, there are 1 phosphorus atom and 4 oxygen atoms, totaling 5 entities when considering the charge.
In short, a single molecule of hydrogen sulfide contains 3 atoms (2 hydrogen and 1 sulfur), while one phosphate ion consists of 5 entities, representing 1 phosphorus atom and 4 oxygen atoms along with the charge.