Question 1

Which scientist is credited with predicting the properties of undiscovered elements and organizing the periodic table based on both atomic mass and chemical properties?

Accepted Answer

Dmitri Mendeleev

Question 2

What is the formula for calculating the effective nuclear charge ($$Z_{	ext{eff}}) $$experienced by a valence electron?

Accepted Answer

$$Z_{	ext{eff}} = Z - S$$

Question 3

Which of the following statements about the periodic trend in atomic radius is correct?

Accepted Answer

Atomic radius decreases from left to right across a period.

Question 4

Why are cations smaller than their parent atoms?

Accepted Answer

Cations lose their outermost electrons, reducing electron-electron repulsion.

Question 5

Which of the following ions is the smallest in the isoelectronic series: $$\mathrm{O$$^{2-}$$}$$, $$\mathrm{F^-}$$, $$\mathrm{Na^+}$$, $$\mathrm{Mg$$^{2+}$$}$$?

Accepted Answer

$$\mathrm{Mg$$^{2+}$$}$$

Question 6

Which property generally increases across a period from left to right for main group elements?

Accepted Answer

Ionization energy

Question 7

A certain element has a very high first ionization energy and a positive electron affinity. Which group is it most likely to belong to?

Accepted Answer

Group 8A (noble gases)

Question 8

Which of the following best explains why the second ionization energy of sodium is much higher than the first?

Accepted Answer

The second electron is removed from a core (noble gas) configuration.

Question 9

Which of the following oxides is most likely to be basic?

Accepted Answer

$$\mathrm{Na_2O}$$

Question 10

Which element is a metalloid and is widely used as a semiconductor in computer chips?

Accepted Answer

Silicon

Question 11

Which of the following best describes the trend in electron affinity across a period?

Accepted Answer

Electron affinity becomes more negative.

Question 12

Which alkali metal reacts with oxygen to form a superoxide ($$\mathrm{MO_2$}) $$rather than a simple oxide or peroxide?

Accepted Answer

Potassium

Question 13

A sample of an unknown element is a dull, brittle solid and a poor conductor of electricity. Which type of element is it most likely to be?

Accepted Answer

Nonmetal

Question 14

Which of the following statements about hydrogen is correct?

Accepted Answer

Hydrogen is a nonmetal and can form hydride anions ($$\mathrm{H^-}) $$when reacting with metals.

Question 15

Which of the following best explains why the reactivity of alkali metals increases down the group?

Accepted Answer

Valence electrons are further from the nucleus and more easily removed.

Question 16

Which of the following is a correct statement about the chemical behavior of Group 7A elements (halogens)?

Accepted Answer

They have highly negative electron affinities and form anions.

Question 17

Which of the following best describes the electron configuration change when a magnesium atom forms a $$\mathrm{Mg$$^{2+}$$}$$ ion?

Accepted Answer

It loses two electrons from the 3s orbital.

Question 18

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have full valence electron shells.

Question 19

Which of the following is a real-world application of the periodic trends in flame tests?

Accepted Answer

Identifying the presence of specific alkali metals in fireworks by their characteristic flame colors.

Question 20

Which of the following best describes the trend in metallic character within Group 6A elements as you move down the group?

Accepted Answer

Metallic character increases.

Periodic Properties of the Elements: Structured Study Notes

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