Polar and Non Polar Covalent Molecules, Polar vs. Nonpolar - CLEAR & SIMPLE

Summary

In this video, Mr. Post explains the concept of molecular polarity, focusing on how to determine whether a molecule is polar or non-polar based on its shape and symmetry. The key takeaway is that molecules with symmetrical shapes tend to be non-polar, while those with asymmetrical shapes, like bent or trigonal pyramidal, are always polar. The lesson highlights various examples, such as BF₃ (non-polar) and H₂O (polar), and emphasizes the importance of symmetry in predicting molecular polarity. Understanding molecular shape and symmetry is crucial for classifying molecules as polar or non-polar.

Takeaways

• 😀 Molecular polarity depends on the symmetry of the molecule and the polarity of its bonds.
• 😀 Non-polar molecules have symmetrical shapes and lack a positive and negative side, like BF₃.
• 😀 Polar molecules have asymmetrical shapes, creating a dipole with one side positive and the other negative.
• 😀 Bent and trigonal pyramidal shapes are always polar because of their asymmetry.
• 😀 Symmetrical shapes, like tetrahedral or linear, can be either polar or non-polar depending on the molecule’s structure.
• 😀 The bond polarity in a molecule can influence how polar it is, but symmetry is the key determinant of polarity.
• 😀 Molecules with identical atoms or bonds, like CO₂, tend to be non-polar because they have no dipole moment.
• 😀 Asymmetrical molecules with different atoms, like H₂O, are polar due to their uneven charge distribution.
• 😀 Trigonal planar molecules can be non-polar if the atoms around the central atom are the same, but polar if different.
• 😀 A molecule's shape can be predicted using its Lewis structure, which helps determine its polarity.
• 😀 The main takeaway is that you can classify a molecule as polar or non-polar based primarily on its symmetry.

Q & A

What is the primary goal of the video on molecular polarity?

The primary goal is to help viewers classify molecules as either polar or non-polar based on their shape and symmetry.

What are the two key factors that determine molecular polarity?

Molecular polarity is determined by two factors: the symmetry of the molecule and the polarity of the bonds between atoms.

How does the symmetry of a molecule affect its polarity?

Symmetrical molecules are typically non-polar because they don't have distinct positive and negative ends, while asymmetrical molecules are often polar due to an imbalance in charge distribution.

What is the difference between molecular polarity and bond polarity?

Molecular polarity refers to the overall charge distribution across a molecule, while bond polarity refers to the uneven sharing of electrons between two atoms in a bond. The focus here is on the symmetry of the whole molecule.

What is the defining feature of a non-polar molecule?

A non-polar molecule does not have distinct positive and negative sides. It typically has a symmetrical shape, such as trigonal planar, where the bonds cancel each other out.

Can a molecule with polar bonds still be non-polar? Provide an example.

Yes, a molecule with polar bonds can still be non-polar if the molecule is symmetrical and the dipoles cancel each other out. For example, BF₃ (Boron Trifluoride) has polar bonds but is non-polar due to its symmetrical trigonal planar shape.

Why are bent and trigonal pyramidal molecules always polar?

Bent and trigonal pyramidal molecules are always polar because they have an asymmetrical shape, which leads to an unequal distribution of charge, creating a dipole with a positive and negative side.

How do lone pairs of electrons affect the polarity of a molecule?

Lone pairs of electrons on the central atom cause the molecule to adopt an asymmetrical shape, which can lead to polarity. For example, trigonal pyramidal molecules have lone pairs that make them polar.

What makes a tetrahedral molecule polar or non-polar?

A tetrahedral molecule can be either polar or non-polar depending on the symmetry of the atoms attached to the central atom. If all attached atoms are the same, it is non-polar; if they are different, it is polar.

What is the significance of the molecular shapes 'linear' and 'bent' when determining polarity?

A linear shape can be either polar or non-polar depending on the symmetry of the atoms at both ends. A bent shape is always polar because it is asymmetrical, creating a dipole with different charge distributions on each side.