Because the amount of screening of the nucleus is related to distance from the n

Question

Because the amount of screening of the nucleus is related to distance from the nucleus, the s and p subshells of a many-electron atom with the same value of n are not of equal energy, as they are in hydrogen. An electron in the p subshell has a lower probability of being inside the electrons of the n=1 shell than does an electron in the s subshell. Thus, the nucleus is screened somewhat more completely for electrons in the p subshell than for electrons in the s subshell. This makes states in the p subshell of higher energy than states in the s subshell. The electron structure of an atom shows how many electrons are in each subshell. For instance, helium's electron structure is written 1s2, signifying the two electrons in the 1s subshell. Neon, with ten electrons, has electron structure 1s22s22p6, signifying two electrons in the 1s subshell, two in the 2s subshell, and six in the 2p subshell. Observe that the exponents sum to the number of electrons in the atom. Which of the following is not a valid electron structure for an atom in its ground state? Use the fact that electrons fill the lowest energy states first and keep in mind the number of allowed states for each subshell.

For states with larger values of n that admit a d subshell, the d subshell is at even higher energy than the p subshell. In fact, its energy is higher than that of the s subshell for the n+1 state. With this in mind, which of the following are valid ground-state electron structures?

1. 1s22s22p63s23p63d2

2. 1s22s22p63s23p63d11

3. 1s22s22p63s23p64s23d5

For states with larger values of  that admit a  subshell, the  subshell is at even higher energy than the  subshell. In fact, its energy is higher than that of the  subshell for the  state. With this in mind, which of the following are valid ground-state electron structures?

(Figure 1) The structure of the periodic table is based on the order in which electron subshells are filled with increasing atomic number Z. You know that the first two electrons go into the 1s subshell and correspond to hydrogen and helium (red in the top row). The next two electrons go into the 2s subshell. The elements with Z=3and Z=4 are lithium and beryllium, respectively (red, second row). The periodic table shown in the figure has each element colored based on the subshell in which the highest-energy electron is found. Which of the following correctly pairs the colors with the subshells that they indicate?

Explanation / Answer

1.A. 1s22s22p63s3

B.1s32s32p63s23p4

2. electrons are enter into increasing order of n+l values

3. 1s22s22p63s23p64s23d5

3. F. 2 and 3

4. red=s yellow=d blue=p

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