Question

question 24 (1 point)
how does atomic radius change from left to right across a period in the periodic table?
o a it tends to increase.
o b it first decreases, then increases.
o c it tends to decrease.
o d it first increases, then decreases.

question 25 (2 points)
what causes the shielding effect to remain constant across a period?
o a electrons are added to the same principal energy level.
o b the charge on the nucleus is constant.
o c the atomic radius increases.
o d electrons are added to different principal energy levels.

question 26 (1 point)
atomic size generally
o a decreases as you move from left to right across a period
o b decreases as you move from top to bottom within a group.
o c increases as you move from left to right across a period.
o d remains constant within a period.

Explanation:

• Question 24: As we move from left to right across a period in the periodic table, the number of protons in the nucleus increases. This leads to a greater positive charge attracting the electrons more strongly. Since electrons are added to the same principal energy level (so there is no significant increase in shielding), the atomic radius tends to decrease.
• Question 25: Shielding effect is related to the number of inner - shell electrons. When electrons are added to the same principal energy level (across a period), the number of inner - shell electrons (which cause shielding) does not change. So, the shielding effect remains constant.
• Question 26: The atomic size (atomic radius) decreases as you move from left to right across a period due to the increased nuclear charge pulling the electrons closer. As you move from top to bottom within a group, the atomic size increases because electrons are added to higher principal energy levels.

Answer:

• Question 24: C. It tends to decrease.
• Question 25: A. Electrons are added to the same principal energy level.
• Question 26: A. decreases as you move from left to right across a period.