determine the correct molecular shapes of XeF4, GeF4, and SeF4
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To determine the molecular shapes of XeF4, GeF4, and SeF4, we need to consider their electron geometries and the presence of lone pairs on the central atom.
1) XeF4:
The electron geometry of XeF4 is octahedral. This means that the central xenon atom is surrounded by six electron groups. Out of these six electron groups, four are bonding pairs coming from the four surrounding fluorine atoms, and the remaining two are lone pairs on the xenon atom. To determine the molecular shape, we only consider the positions of the atoms and disregard the lone pairs. Therefore, the molecular shape of XeF4 is square planar, where the four fluorine atoms are positioned around the central xenon atom in a flat square shape.
2) GeF4:
The electron geometry of GeF4 is also octahedral, just like XeF4. Similar to XeF4, the central germanium (Ge) atom is surrounded by four bonding pairs and two lone pairs. However, unlike XeF4, in GeF4, the lone pairs are more dominant due to the larger size of germanium compared to xenon. The presence of lone pairs affects the molecular shape. So, the molecular shape of GeF4 is distorted or seesaw-shaped, where the four fluorine atoms are positioned in a tetrahedral shape with the two lone pairs taking up the remaining positions above and below the plane.
3) SeF4:
The electron geometry of SeF4 is also octahedral. However, in this molecule, the central selenium (Se) atom is surrounded by four bonding pairs and only one lone pair. The molecular shape is determined by considering the positions of the atoms and ignoring the lone pair. So, the molecular shape of SeF4 is trigonal bipyramidal. The four fluorine atoms are positioned in a trigonal plane around the central selenium atom, while the lone pair is located above or below the plane, giving a three-sided pyramid shape.
Remember, to determine the molecular shapes, it is important to first determine the electron geometry by considering all the electron groups (bonding pairs and lone pairs) around the central atom. Then, we consider the positions of the atoms and exclude the lone pairs to determine the molecular shape.