Final answer:
To indicate bond polarity, arrows point towards the more electronegative atom. For F-CH3, the arrow points towards F; for H3C-NH2, it points towards NH2; for Br—MgCH3, it points towards Br.
Step-by-step explanation:
The student is asking about the polarity of bonds in different compounds, specifically F-CH3, H3C-NH2, and Br—MgCH3. The direction of the bond polarity is determined by the difference in electronegativity between the atoms forming the bond. A bond is polarized towards the more electronegative atom.
For F-CH3 (fluoromethane), the arrow would point from CH3 to F because fluorine is more electronegative than carbon. For H3C-NH2 (methylamine), the arrow would point from CH3 to NH2 as nitrogen is more electronegative than carbon. For Br—MgCH3 (methylmagnesium bromide), the arrow would point from MgCH3 to Br because bromine is more electronegative than magnesium.
A dipole arrow is drawn with a cross (like a plus sign) at the less electronegative end, indicating a partial positive charge, and the arrowhead points towards the more electronegative atom, indicating a partial negative charge. The arrow shows the direction of electron flow, from the less electronegative atom to the more electronegative atom.