Question 1

Which quantum number is directly associated with the electron's spin, and what are its possible values?

Accepted Answer

$$m_s$$, possible values: $$+\frac{1}{2}, -\frac{1}{2}$$

Question 2

According to the Pauli Exclusion Principle, which of the following sets of quantum numbers is NOT allowed for two electrons in the same atom?

Accepted Answer

$$n=2,\ l=1,\ m_l=1,\ m_s=+\frac{1}{2}$$ and $$n=2,\ l=1,\ m_l=1,\ m_s=+\frac{1}{2}$$

Question 3

Which of the following correctly represents the ground state electron configuration for sulfur ($$Z=16$$)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^4$$

Question 4

Which principle explains why electrons fill the lowest available energy orbitals before occupying higher ones?

Accepted Answer

Aufbau Principle

Question 5

For a given atom, which subshell has the greatest penetration and why?

Accepted Answer

$$s$$ subshell, because it has the highest effective nuclear charge ($$Z_{	ext{eff}})$$

Question 6

Which of the following ions is isoelectronic with neon ($$Ne$$)?

Accepted Answer

$$Na^+$$

Question 7

Arrange the following species in order of increasing first ionization energy: $$Cl$$, $$Ca$$, $$Mg$$, $$S.$$

Accepted Answer

$$Ca \u003c Mg \u003c S \u003c Cl$$

Question 8

Which of the following best describes Hund's Rule?

Accepted Answer

Electrons fill orbitals of the same energy singly before pairing up.

Question 9

What is the electron configuration for the $$Fe^{2+}$$ ion ($$Z=26$$)?

Accepted Answer

$$[Ar]\ 3d^6$

Question 10

Which of the following statements about the order of orbital energies in multi-electron atoms is correct?

Accepted Answer

$$4s is $$filled before $$3d$$ because $$4s$$ has lower energy in neutral atoms.

Question 11

Which of the following is a correct set of quantum numbers for an electron in a $$3p$$ orbital?

Accepted Answer

$$n=3,\ l=1,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 12

Which element has the ground state electron configuration $$[Ne]\ 3s^2$\ 3p^3$?

Accepted Answer

Phosphorus ($$P)$$

Question 13

Why does the $$4s$$ orbital fill before the $$3d$$ orbital in the ground state of potassium ($$K$$)?

Accepted Answer

The $$4s$$ orbital has a lower energy than the $$3d$$ orbital in neutral atoms.

Question 14

Which of the following ions is isoelectronic with $$Mg^{2+}$$?

Accepted Answer

$$O^{2-}$$

Question 15

A sample of hydrogen atoms is passed through a non-uniform magnetic field, resulting in two distinct beams. What property of the electron does this experiment demonstrate?

Accepted Answer

Electron spin quantum number ($$m_s)$$

Question 16

Which of the following best explains why $$d$$ and $$f$$ orbitals have poorer penetration compared to $$s$$ and $$p$$ orbitals?

Accepted Answer

Higher $$l$$ value leads to greater angular momentum, keeping electrons further from the nucleus.

Question 17

Which of the following is the correct electron configuration for the $$Cu^+$$ ion?

Accepted Answer

$$[Ar]\ 3d$$^{10}$$

Question 18

Which of the following statements about valence electrons is correct?

Accepted Answer

Valence electrons are the electrons in the outermost shell of an atom and are involved in chemical bonding.

Question 19

Which of the following is the correct order of filling for the first ten atomic orbitals according to the Aufbau principle?

Accepted Answer

$$1s \rightarrow 2s \rightarrow 2p \rightarrow 3s \rightarrow 3p \rightarrow 4s \rightarrow 3d \rightarrow 4p \rightarrow 5s \rightarrow 4d$$

Quantum Numbers, Electron Configuration, and Periodic Trends in Multi-Electron Atoms

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