To draw the Lewis structure for the thiocyanate ion (SCN-1), we start by determining the total number of valence electrons. Carbon (C) has 4 valence electrons, sulfur (S) has 6 valence electrons, and nitrogen (N) has 5 valence electrons. Since the SCN ion has a -1 charge, we add one additional electron. Therefore, the total number of valence electrons is:
Total Valence Electrons: 4 (C) + 6 (S) + 5 (N) + 1 (charge) = 16 electrons.
Now, let’s move on to the total number of electron groups. In SCN, we have three main atoms connected by bonds. The arrangement is as follows:
Electron Groups: We have 3 electron groups: one single and one triple bond (C≡N) and a single bond to sulfur (C-S).
Next, we determine the electron geometry. The geometry is dictated by the arrangement of these electron groups:
Electron Geometry: The electron geometry around the central carbon atom resembles a linear shape due to the triple bond with nitrogen and the single bond with sulfur.
Following that, we examine the molecular shape. The arrangement of the bonded atoms gives the overall molecular shape:
Molecular Shape: Linear, as the bonding pairs are arranged in a straight line.
Now, let’s discuss molecular polarity. To ascertain if a molecule is polar, we consider the electronegativity of the atoms involved and their spatial arrangement:
Molecular Polarity: The SCN ion is polar because it has a linear shape with different electronegativities between carbon, sulfur, and nitrogen. The dipole moment doesn’t cancel out, resulting in a polar molecule.
Finally, we identify the major types of attractive forces present:
Major Attractive Force: The primary attractive forces in thiocyanate ions include dipole-dipole interactions due to the polar nature of the molecule, along with potential hydrogen bonding when interacting with polar solvents.