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2. what trends do you notice for the atomic radii of group 2a? 3. what …

Question

  1. what trends do you notice for the atomic radii of group 2a?
  2. what trends do you notice for the atomic radii of period 3?
  3. explain why this trend occurs.
  4. ionization energy is the amount of energy required to remove an electron from an element. using the ionization energies of the elements in period 2 listed below, make a line graph the values vs. atomic number.
elementie (kj/mole)period 2elementie (kj/mole)
be900o1314
b799f1682
c1088ne2080
  1. on the same graph, make a line graph the first three atoms in group 2a listed below in a different color.
elementie (kj/mole)group 2a
mg736
ca590

graph grid: y - axis ionization energy (300, 600, 900, 1200, 1500, 1800, 2100), x - axis atomic number (1 - 20)

  1. what trend do you notice for the ionization energies in period 2?
  2. what trend do you notice for the ionization energies of group 2a?
  3. explain why this trend occurs.

Explanation:

Response
Question 2:
Brief Explanations

Group 2A elements are alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra). As we move down Group 2A (from top to bottom), the atomic number increases, and new electron shells are added. Each subsequent element has one more electron shell than the previous one. For example, Be has electron configuration $1s^2 2s^2$, Mg has $1s^2 2s^2 2p^6 3s^2$, so Mg has an additional shell (n=3 compared to Be's n=2). The addition of electron shells increases the distance between the nucleus and the outermost electrons, and the shielding effect from inner electrons also increases, reducing the effective nuclear charge experienced by the outermost electrons. This leads to an increase in atomic radius as we go down the group.

Brief Explanations

Period 3 elements are Na, Mg, Al, Si, P, S, Cl, Ar. As we move across Period 3 from left to right (increasing atomic number), the number of protons in the nucleus increases (nuclear charge increases), while the electrons are added to the same valence shell (n=3 for Period 3). The increase in nuclear charge pulls the valence electrons more strongly towards the nucleus. There is no significant increase in the shielding effect because the electrons are added to the same shell, so the effective nuclear charge experienced by the valence electrons increases. This causes the atomic radius to decrease as the electrons are pulled closer to the nucleus.

Brief Explanations

For atomic radius trends, two main factors are effective nuclear charge ($Z_{eff}$) and number of electron shells (n).

  • Across a period (left to right): Atomic number (number of protons) increases, so nuclear charge increases. Electrons are added to the same valence shell (same n), so shielding from inner electrons does not increase significantly. Thus, $Z_{eff}$ increases, pulling valence electrons closer to the nucleus, decreasing atomic radius.
  • Down a group (top to bottom): Atomic number increases, and electrons are added to new shells (n increases). The increase in n (more electron shells) increases the distance between the nucleus and valence electrons. Also, inner electron shells shield the valence electrons from the nucleus, reducing $Z_{eff}$ on valence electrons. Both factors (more shells, increased shielding) cause the atomic radius to increase.

The question likely refers to the trend across a period (since Question 3 is about Period 3) or down a group (Question 2 about Group 2A). For Period 3 (left to right), the trend (decrease) occurs because of increasing nuclear charge with electrons in the same shell, increasing $Z_{eff}$. For Group 2A (top to bottom), the trend (increase) occurs because of increasing n (more shells) and increased shielding, decreasing $Z_{eff}$ on valence electrons.

Answer:

As we move down Group 2A (from top to bottom), the atomic radii increase. This is because each successive element has an additional electron shell, increasing the distance between the nucleus and the outermost electrons, and the shielding effect from inner electrons reduces the effective nuclear charge on the outer electrons, allowing them to be further from the nucleus.

Question 3: