Assertion: Alkenes undergo electrophilic addition whereas aldehydes and ketones undergo nucleophilic addition. 

Reason: In alkenes the double bond joins two carbon atoms and there is no resultant polarity. In carbonyl compounds, the carbonyl group is highly polar and the high partial positive charge on the C atom makes it susceptible to nucleophilic attack. Alkenes undergo electrophilic addition whereas aldehydes and ketones undergo nucleophilic addition.

Both Assertion and Reason are correct and the Reason is the correct explanation for the Assertion.

The correct answer is option 1. Both Assertion and Reason are correct and the Reason is the correct explanation for the Assertion.

The assertion correctly states that alkenes undergo electrophilic addition reactions. The double bond in alkenes consists of two carbon atoms connected by a sigma bond and a pi bond. The pi bond, which is formed by the overlap of p-orbitals, has an electron-rich region. This region can act as a nucleophile and attack electrophiles, resulting in electrophilic addition reactions. Examples of electrophilic addition reactions of alkenes include reactions with hydrogen halides (H-X) or halogens (X₂).

The reason provided for the assertion is correct. Carbonyl compounds, such as aldehydes and ketones, have a highly polar carbonyl group (C=O). The oxygen atom is more electronegative than the carbon atom, creating a partial negative charge on oxygen and a partial positive charge on carbon. This partial positive charge makes the carbonyl carbon susceptible to nucleophilic attack. Nucleophiles can attack the carbon atom of the carbonyl group, leading to nucleophilic addition reactions. Common nucleophiles that react with carbonyl compounds include Grignard reagents (RMgX) and organolithium compounds (RLi).

Therefore, the reason provided, which explains the polarity and nucleophilic susceptibility of carbonyl compounds compared to alkenes, correctly supports the assertion that alkenes undergo electrophilic addition, while aldehydes and ketones undergo nucleophilic addition.