Question

a. reactivity for non - metals (group 17)
electronegativity decreases down the group because there is more shielding and less pull from the nucleus. fluorine is the most reactive because it is higher up on the group/family.
summary questions:

1. how does the number of protons influence the atomic radius across a period?
2. how does atomic radius relate to an element’s ability to attract electrons?
3. why do metals become less reactive across a period but more reactive down a group?
4. why do nonmetals become more reactive across a period but less reactive down a group?

Explanation:

Step1: Understand nuclear - charge concept

As we move across a period, the number of protons in the nucleus increases. This increases the nuclear charge. The electrons are added to the same energy level. The increased nuclear charge pulls the electrons closer, thus decreasing the atomic radius. For example, from sodium to chlorine in period 3, the number of protons increases from 11 to 17, and the atomic radius decreases.

Step2: Analyze electron - attraction ability

Atoms with a smaller atomic radius have a stronger ability to attract electrons. This is because the out - ermost electrons are closer to the positively charged nucleus. For instance, fluorine has a small atomic radius and high electronegativity, meaning it can attract electrons strongly in a chemical bond.

Step3: Consider metal reactivity trends

Across a period, metals become less reactive because the increased nuclear charge makes it harder for them to lose electrons. Down a group, the atomic radius increases due to the addition of new energy levels. The outermost electrons are farther from the nucleus and are more easily lost, making the metal more reactive. For example, potassium is more reactive than sodium.

Step4: Analyze non - metal reactivity trends

Across a period, nonmetals become more reactive as the nuclear charge increases and they are closer to achieving a full outer shell by gaining electrons. Down a group, nonmetals become less reactive because the atomic radius increases and the outermost electrons are farther from the nucleus, making it harder to attract additional electrons. For example, chlorine is more reactive than bromine.

Answer:

1. As the number of protons increases across a period, the nuclear charge increases, pulling the electrons closer and decreasing the atomic radius.
2. Atoms with a smaller atomic radius have a stronger ability to attract electrons as the outermost electrons are closer to the positively - charged nucleus.
3. Across a period, metals become less reactive as the increased nuclear charge makes it harder to lose electrons. Down a group, the atomic radius increases, making it easier to lose electrons and increasing reactivity.
4. Across a period, nonmetals become more reactive as the nuclear charge increases and they are closer to achieving a full outer shell by gaining electrons. Down a group, nonmetals become less reactive as the atomic radius increases and it becomes harder to attract electrons.