Passage
Dmitri Mendeleev is credited with grouping the elements by atomic mass and observing that similar properties emerge periodically. Henry Moseley then determined that a fundamental property, which Ernest Rutherford later called the atomic number, is more important than atomic mass for ordering the elements.As the periodic table took shape, scientists noted certain properties and trends. For example, Rayleigh and Ramsay observed that some elements are unreactive and gave them the name noble gases. But it was not until Niels Bohr described his model of the atom that scientists understood why noble gases are stable.Another important trend was discovered by Linus Pauling. He was the first to identify electronegativity as a way to describe bonds that are neither completely ionic nor completely covalent. Pauling assigned fluorine the highest electronegativity value of 4.0 because of its strong tendency to attract electrons when bonded to other atoms. All other atoms were assigned values relative to fluorine. This became known as the Pauling electronegativity scale.Scientists identified other trends based on x-ray crystallography and reactivity studies. Figure 1 shows the first ionization energy of the elements, and Figure 2 shows electron affinity.
Figure 1 First ionization energy of elements
Figure 2 Electron affinity of several elements (larger negative values indicate greater electron affinity)
-The difference between the first and second ionization energies for magnesium is approximately 700 kJ/mol. The difference between the second and third ionization energies will likely be:

Question

Passage
Dmitri Mendeleev is credited with grouping the elements by atomic mass and observing that similar properties emerge periodically. Henry Moseley then determined that a fundamental property, which Ernest Rutherford later called the atomic number, is more important than atomic mass for ordering the elements.As the periodic table took shape, scientists noted certain properties and trends. For example, Rayleigh and Ramsay observed that some elements are unreactive and gave them the name noble gases. But it was not until Niels Bohr described his model of the atom that scientists understood why noble gases are stable.Another important trend was discovered by Linus Pauling. He was the first to identify electronegativity as a way to describe bonds that are neither completely ionic nor completely covalent. Pauling assigned fluorine the highest electronegativity value of 4.0 because of its strong tendency to attract electrons when bonded to other atoms. All other atoms were assigned values relative to fluorine. This became known as the Pauling electronegativity scale.Scientists identified other trends based on x-ray crystallography and reactivity studies. Figure 1 shows the first ionization energy of the elements, and Figure 2 shows electron affinity.

Figure 1 First ionization energy of elements

Figure 2 Electron affinity of several elements (larger negative values indicate greater electron affinity)
-The difference between the first and second ionization energies for magnesium is approximately 700 kJ/mol. The difference between the second and third ionization energies will likely be:

Quizplus · Accepted Answer

11ecba2d_11c0_430b_a3bf_e7fddbde38e2_MD0008_00 Ionization energy is the energy needed to remove an electron from a ground state gaseous atom or ion. The first, second, and third ionization energies are the energies required to remove the first, second, and third electron, respectively. Because the valence shell is farther away from the positively charged nucleus, electrons in this shell are easier to remove than the inner core electrons. The electrons are removed in order beginning with the electron of highest energy. Magnesium has two electrons in its valence shell (n = 3). Magnesium's third ionization energy is significantly larger because it requires the removal of an electron from the inner core. These electrons are more tightly held than the valence electrons, and therefore require more energy to remove. (Choice A) Although orbital shape does have some effect on ionization energy (eg, s electrons are more tightly held than p electrons), energy differences based on the distance from the nucleus have a much larger effect. In the case of magnesium, the first and second electrons are removed from an s orbital, not a p orbital. (Choice C) "Spin-paired" electrons occur when two electrons occupy the same atomic orbital. Magnesium has two electrons in its valence shell that are spin-paired in the 3s orbital; the third electron is also spin-paired to another electron in one of the 2p orbitals. (Choice D) Electrons are removed beginning with the subshell that is farthest from the nucleus. In the case of magnesium, electrons are removed from the n = 3 subshell first and then from the n = 2 subshell. Educational objective: Ionization energy is the energy required to remove an electron from a ground-state gaseous atom or ion. The first, second, and third ionization energies describe the energy required to remove one, two, or three electrons, beginning with the electron of highest energy. Electrons in the inner core require significantly more energy to remove than valence electrons.

Passage Dmitri Mendeleev Is Credited with Grouping the Elements by Atomic