Question 1

Which statement best describes the concept of 'charge nucléaire effective' ($$Z_{eff}) $$for an electron in a multi-electron atom?

Accepted Answer

It is the net positive charge experienced by an electron, accounting for both the nuclear charge and the shielding by other electrons.

Question 2

Which of the following electron configurations represents the ion $$Al^{3+}$$?

Accepted Answer

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

Question 3

As you move from left to right across a period in the periodic table, what generally happens to the atomic radius?

Accepted Answer

It decreases because the effective nuclear charge increases, pulling electrons closer.

Question 4

Which of the following ions has the smallest ionic radius?

Accepted Answer

$$Al^{3+}$$

Question 5

What is the main reason why the first ionization energy generally increases across a period?

Accepted Answer

The effective nuclear charge increases, holding electrons more tightly.

Question 6

Which element from the second period exhibits properties that differ significantly from other elements in its group due to its small atomic radius and high electronegativity?

Accepted Answer

Fluorine ($$F)$$

Question 7

What is the electron configuration of $$F^{-}$$?

Accepted Answer

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

Question 8

Which of the following best explains why $$Li^+ is $$much smaller than $$Li$$?

Accepted Answer

The loss of an electron reduces electron-electron repulsion and leaves only the first shell occupied.

Question 9

Which of the following ions has the same electron configuration as neon ($$Ne$$)?

Accepted Answer

$$Na^{+}$$

Question 10

What is the effect of increasing the principal quantum number ($$n) on $$the atomic radius within a group?

Accepted Answer

The atomic radius increases because electrons are added to higher energy levels further from the nucleus.

Question 11

Which of the following best describes the diagonal relationship in the periodic table?

Accepted Answer

Certain elements in adjacent groups and periods (diagonally) have similar properties due to comparable charge density and atomic radius.

Question 12

Which of the following is the correct order of increasing first ionization energy for the elements $$K$$, $$Ca$$, $$Br$$, and $$Ge$$?

Accepted Answer

$$K \u003c Ca \u003c Ge \u003c Br$$

Question 13

Why do elements in the same group of the periodic table generally have similar chemical properties?

Accepted Answer

They have the same number of valence electrons.

Question 14

Which of the following best explains the trend in ionic radius for isoelectronic ions $$O^{2-}$$, $$F^{-}$$, $$Na^{+}$$, $$Mg^{2+}$$, and $$Al^{3+}$$?

Accepted Answer

Ionic radius decreases with increasing nuclear charge because electrons are pulled closer to the nucleus.

Question 15

Which of the following elements has the largest atomic radius?

Accepted Answer

Sodium ($$Na)$$

Question 16

What is the main factor that determines the energy required to remove an electron from an atom (ionization energy)?

Accepted Answer

The effective nuclear charge experienced by the electron.

Question 17

Which of the following is true about the electron configuration of transition metal ions?

Accepted Answer

Electrons are always removed from the highest principal quantum number ($$n) $$orbital first.

Question 18

Which of the following best explains why the second period elements (Li to F) often show unique chemical behavior compared to heavier elements in the same group?

Accepted Answer

They have smaller atomic radii and higher charge density, leading to stronger bonding and less ability to expand their valence shell.

Question 19

Which of the following equations correctly represents the first ionization energy process for sodium ($$Na$$)?

Accepted Answer

$$Na \rightarrow Na$$^{+}$$ + e$$^{-}$$

La classification périodique des éléments et ses propriétés

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