Question

explain your answer.

1. why do atoms get smaller going left to right across a period?

1. why do atoms get larger going down a group?

Explanation:

Question 21:

As we move left to right across a period, the atomic number (number of protons) increases. The added protons in the nucleus increase the positive nuclear charge. Electrons are added to the same energy level (shell) across a period. The increased nuclear charge pulls the electrons in the same shell more strongly towards the nucleus, decreasing the atomic radius (making atoms smaller).

When moving down a group, the number of electron shells (energy levels) increases. Each new shell is further from the nucleus than the previous one. Even though the nuclear charge also increases, the additional electron shells are located at greater distances from the nucleus, and the shielding effect of inner electrons reduces the pull of the nucleus on the outermost electrons. This leads to an increase in atomic radius (atoms get larger).

Answer:

As we move left to right across a period, the number of protons in the nucleus increases (increasing nuclear charge), while electrons are added to the same energy level. The stronger nuclear charge pulls the electrons in the same shell more tightly, reducing the atomic radius, so atoms get smaller.

Question 22: