Question 1

Which of the following best explains why Mendeleev’s periodic table was able to predict the properties of undiscovered elements such as gallium?

Accepted Answer

He arranged elements by increasing atomic mass, noticing that similar properties recurred periodically, allowing him to leave gaps for undiscovered elements.

Question 2

Which statement about the modern periodic table is correct?

Accepted Answer

Elements are arranged in order of increasing atomic number, and elements in the same group have similar properties.

Question 3

Which of the following electron configurations represents a violation of the Pauli Exclusion Principle?

Accepted Answer

An orbital diagram with two electrons in the same orbital both having spin up ($$m_s = +\frac{1}{2}).$$

Question 4

Which of the following best describes the concept of effective nuclear charge ($$Z_{	ext{eff}}$$)?

Accepted Answer

The net positive charge experienced by a valence electron after accounting for shielding by core electrons.

Question 5

Which of the following correctly ranks the atomic radii of the elements S, Ca, F, Rb, and Si from largest to smallest?

Accepted Answer

Rb \u003e Ca \u003e Si \u003e S \u003e F

Question 6

Which of the following statements about electron configuration and chemical reactivity is true?

Accepted Answer

Halogens tend to gain one electron to achieve a noble gas configuration.

Question 7

Which of the following best explains why the 4s orbital fills before the 3d orbital in transition metals?

Accepted Answer

The 4s orbital has a lower energy than the 3d orbital due to penetration and shielding effects.

Question 8

Which of the following ions is isoelectronic with argon ($$Ar$$)?

Accepted Answer

$$K^+$$

Question 9

Which of the following elements has the highest first ionization energy?

Accepted Answer

Neon ($$Ne)$$

Question 10

Which of the following best describes the trend in atomic radius as you move down a group in the periodic table?

Accepted Answer

Atomic radius increases due to the addition of higher principal energy levels.

Question 11

Which of the following statements about the electron affinity (EA) of main-group elements is correct?

Accepted Answer

Halogens have the most negative (largest) electron affinities in their periods.

Question 12

Which of the following best explains why cations are smaller than their parent atoms?

Accepted Answer

Cations have fewer electrons, resulting in a greater effective nuclear charge per electron and a smaller radius.

Question 13

Which of the following elements is most likely to be paramagnetic in its ground state?

Accepted Answer

Oxygen ($$O)$$

Question 14

Which of the following best describes the trend in metallic character across a period from left to right?

Accepted Answer

Metallic character decreases due to increasing effective nuclear charge.

Question 15

Which of the following is the correct electron configuration for a ground-state germanium (Ge) atom?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^2$$\ $$3d^{10}$$\ $$4p^2$$

Question 16

Which of the following best explains the exception to the expected electron configuration for chromium ($$Cr$$)?

Accepted Answer

Chromium has a half-filled $$3d$$ subshell and a half-filled $$4s$$ orbital, which is more stable than the expected configuration.

Question 17

Which of the following best describes the trend in first ionization energy as you move across a period from left to right?

Accepted Answer

First ionization energy increases due to increasing effective nuclear charge.

Question 18

Which of the following best explains why the addition of an electron to a Group 2A element is endothermic?

Accepted Answer

The added electron must enter a higher energy subshell, which is less stable and requires energy input.

Question 19

Which of the following statements about the periodic trend in ionic radii is correct?

Accepted Answer

For isoelectronic species, the ion with the largest positive charge is the smallest.

Chapter 3: Periodic Properties of the Elements – Study Notes

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