Chapter 7: Problem 131
Choose the larger atom in each pair: (a) \(\mathrm{Mg}\) or \(\mathrm{S} ;\) (b) As or Bi.
Short Answer
Expert verified
The larger atoms in each pair are (a) Mg and (b) Bi.
Step by step solution
01
Understanding Atomic Size Trend on the Periodic Table
The size of an atom generally increases as you move from top to bottom in a group of the periodic table and decreases as you move from left to right across a period. This is due to the increase in the number of electron shells as the atomic number increases, and the increase in nuclear charge attracting electrons closer to the nucleus across a period.
02
Comparing Atomic Size for Pair (a)
Mg (Magnesium) is located in period 3, group 2 of the periodic table, while S (Sulfur) is in period 3, group 16. Both are in the same period, but S is to the right of Mg. Thus, Mg will be larger than S since atomic size decreases across a period.
03
Comparing Atomic Size for Pair (b)
As (Arsenic) is located in period 4, group 15, while Bi (Bismuth) is in period 6, group 15. Both belong to the same group, but Bi is below As. Therefore, Bi will be larger than As because atomic size increases down a group.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Periodic Table Groups
Understanding periodic table groups is essential for grasping trends in atomic size. Each group consists of elements with the same number of electrons in their outermost shell, known as valence electrons. These electrons play a critical role in chemical bonding and reactivity.
In terms of atomic size, elements increase in size as you move down a group. This is because with each additional period, a new electron shell is added to the atoms, increasing the distance between the outermost electrons and the nucleus. Despite the increasing positive charge of the nucleus that accompanies added protons, the effect of shell shielding and increased electron-electron repulsion in the larger atoms outweighs the attraction of electrons to the nucleus. Therefore, an element like Bismuth in group 15 will have a larger atomic radius than Arsenic, which is higher up in the same group.
Additionally, the presence of more electron shells also means more repulsion between electrons, causing the electron clouds to expand and thus pushing the overall size of the atom to increase. This accounts for the size difference between Magnesium and Bismoor, despite both being in the same period.
In terms of atomic size, elements increase in size as you move down a group. This is because with each additional period, a new electron shell is added to the atoms, increasing the distance between the outermost electrons and the nucleus. Despite the increasing positive charge of the nucleus that accompanies added protons, the effect of shell shielding and increased electron-electron repulsion in the larger atoms outweighs the attraction of electrons to the nucleus. Therefore, an element like Bismuth in group 15 will have a larger atomic radius than Arsenic, which is higher up in the same group.
Additionally, the presence of more electron shells also means more repulsion between electrons, causing the electron clouds to expand and thus pushing the overall size of the atom to increase. This accounts for the size difference between Magnesium and Bismoor, despite both being in the same period.
Electron Shells
Electron shells are like the layers of an onion around the nucleus of an atom, where electrons reside. Each shell corresponds to a principal energy level, and atoms can have multiple shells. As we go from the center (nucleus) to the outside of an atom, electrons fill shells in an order based on increasing energy.
Atoms grow in size mainly because these shells are added, which occurs as one moves down a group in the periodic table. The more shells an atom has, the larger it is, because outer shells are located farther from the nucleus and occupy more space. For instance, Bismuth has more electron shells than Arsenic, which makes its atomic radius larger.
This concept helps explain why Magnesium, despite having a similar electron configuration in the outer shell as Sulfur, has a larger atomic radius - Magnesium has its valence electrons in a shell closer to the nucleus than the corresponding valence shell of Sulfur.
Atoms grow in size mainly because these shells are added, which occurs as one moves down a group in the periodic table. The more shells an atom has, the larger it is, because outer shells are located farther from the nucleus and occupy more space. For instance, Bismuth has more electron shells than Arsenic, which makes its atomic radius larger.
This concept helps explain why Magnesium, despite having a similar electron configuration in the outer shell as Sulfur, has a larger atomic radius - Magnesium has its valence electrons in a shell closer to the nucleus than the corresponding valence shell of Sulfur.
Periodic Table Periods
Periods on the periodic table are horizontal rows that represent elements with the same number of electron shells but increasing number of electrons within the valence shell as you move from left to right. This arrangement reflects an increase in the atomic number and subsequently, the positive charge in the nucleus.
As you traverse a period from left to right, the atomic size decreases. This might seem counterintuitive because more protons in the nucleus usually mean a stronger pull on the electrons, which should increase the size. However, the increased nuclear charge combined with a relatively constant distance to the outermost electrons results in a tighter grip on those electrons, effectively pulling them closer and reducing the size of the atom.
For Magnesium and Sulfur, which reside in the same period, their difference in size is thus attributed to the number of protons and the resulting increase in electrostatic attraction between the nucleus and the valence electrons as one moves to the right. Magnesium, being further left, has fewer protons and a larger size compared to Sulfur.
As you traverse a period from left to right, the atomic size decreases. This might seem counterintuitive because more protons in the nucleus usually mean a stronger pull on the electrons, which should increase the size. However, the increased nuclear charge combined with a relatively constant distance to the outermost electrons results in a tighter grip on those electrons, effectively pulling them closer and reducing the size of the atom.
For Magnesium and Sulfur, which reside in the same period, their difference in size is thus attributed to the number of protons and the resulting increase in electrostatic attraction between the nucleus and the valence electrons as one moves to the right. Magnesium, being further left, has fewer protons and a larger size compared to Sulfur.
