Question 1

Which statement best describes the main insight from Rutherford's gold foil experiment?

Accepted Answer

Most of the atom is empty space with a dense, positively charged nucleus at the center.

Question 2

Which of the following is a correct representation of an isotope of magnesium with 13 neutrons?

Accepted Answer

$$\$$displaystyle ^{25}$$_{12}\mathrm{Mg}$$

Question 3

Which group on the periodic table contains elements that are highly reactive metals and react vigorously with water?

Accepted Answer

Group 1A (Alkali metals)

Question 4

What is the total number of electrons in the third energy level of a phosphorus atom ($$\displaystyle Z=15$$)?

Accepted Answer

5

Question 5

Which of the following best explains why ionization energy increases across a period from left to right?

Accepted Answer

The nuclear charge increases, pulling electrons closer and making them harder to remove.

Question 6

A neutral atom of chlorine has a mass number of 37. How many neutrons does it contain?

Accepted Answer

20

Question 7

Which of the following elements is classified as a metalloid?

Accepted Answer

Boron (B)

Question 8

According to Bohr’s atomic model, what happens when an electron moves from a higher energy level to a lower energy level?

Accepted Answer

The atom emits a photon of energy.

Question 9

Which of the following is the correct Lewis dot structure for magnesium (Mg)?

Accepted Answer

$$\displaystyle \mathrm{Mg}\,\cdot\,\cdot$$

Question 10

Which element would have the largest atomic radius among the following?

Accepted Answer

Potassium (K)

Question 11

Which of the following statements is NOT part of Dalton’s atomic theory?

Accepted Answer

Atoms are made of protons, neutrons, and electrons.

Question 12

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

Accepted Answer

Atomic size increases due to the addition of energy levels.

Question 13

A sample contains $$\displaystyle 78.70\%$$ $$\$$displaystyle ^{24}$$_{12}\mathrm{Mg}$$, $$\displaystyle 10.13\%$$ $$\$$displaystyle ^{25}$$_{12}\mathrm{Mg}$$, and $$\displaystyle 11.17\%$$ $$\$$displaystyle ^{26}$$_{12}\mathrm{Mg}. $$What is the average atomic mass of magnesium? (Round to two decimal places)

Accepted Answer

$$\displaystyle 24.31\ \mathrm{amu}$$

Question 14

Which of the following elements is a major element in the human body?

Accepted Answer

Oxygen (O)

Question 15

Which of the following best explains why the alkali metals are stored under oil in the laboratory?

Accepted Answer

They are highly reactive with water and air.

Question 16

Which of the following is the correct electron configuration for a neutral atom of sodium ($$\displaystyle Z=11$$)?

Accepted Answer

$$\displaystyle 2,8,1$$

Question 17

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

Accepted Answer

Ionization energy decreases due to increased atomic radius.

Question 18

Which of the following is a property of halogens?

Accepted Answer

They are highly reactive nonmetals.

Question 19

Which of the following best explains why isotopes of the same element have different mass numbers?

Accepted Answer

They have different numbers of neutrons.

Question 20

Which of the following best describes the relationship between wavelength and energy in the electromagnetic spectrum?

Accepted Answer

As wavelength increases, energy decreases.

Atoms & Elements: Periodic Trends and Atomic Structure

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