Question

1. why does electronegativity increase when you move from left to right across a row of the periodic table?

the force the nucleus exerts on electrons decreases.
the distance from the nucleus to the bond increases.
the number of protons in the nucleus increases.
the number of electron shells decreases.

Explanation:

To determine why electronegativity increases left - to - right across a period:

1. Analyze Option 1: If the nuclear force on electrons decreased, electronegativity (attraction for electrons) would not increase. So this is incorrect.
2. Analyze Option 2: As we move left - to - right across a period, the distance from the nucleus to the valence electrons (involved in bonding) generally stays relatively constant (same energy level). An increase in this distance would not lead to higher electronegativity. So this is incorrect.
3. Analyze Option 3: Moving left - to - right across a period, the atomic number (and thus the number of protons in the nucleus) increases. More protons mean a stronger positive charge in the nucleus, which exerts a greater attractive force on electrons (both in the atom's own valence shell and in bonding situations), increasing electronegativity. This makes sense.
4. Analyze Option 4: The number of electron shells remains the same when moving across a period (it increases when moving down a group). So this is incorrect.

Answer:

C. The number of protons in the nucleus increases.