Question 1

Which experiment provided the first direct evidence that atoms contain a small, dense nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 2

Which of the following statements best describes the difference between an atom and an element?

Accepted Answer

An element is composed of atoms, which are the smallest identifiable units of that element.

Question 3

Which of the following is NOT a postulate of Dalton’s atomic theory?

Accepted Answer

Atoms can be divided into protons, neutrons, and electrons.

Question 4

A neutral atom of sodium (Na) has an atomic number of 11. How many protons and electrons does it contain?

Accepted Answer

11 protons and 11 electrons

Question 5

Which property is NOT characteristic of metals?

Accepted Answer

Tends to gain electrons in chemical reactions

Question 6

Which group in the periodic table contains elements that are chemically inert and do not readily form compounds?

Accepted Answer

Noble gases

Question 7

A fluorine atom gains one electron to form an ion. What is the charge of this ion, and what is it called?

Accepted Answer

$$1-$$, anion

Question 8

Which of the following best explains why the atomic mass of chlorine is not a whole number?

Accepted Answer

Chlorine is a mixture of isotopes with different masses.

Question 9

Calculate the atomic mass of gallium given the following data: Ga-69 (mass $$68.9256$$ amu, abundance $$60.11\%) $$and Ga-71 (mass $$70.9247$$ amu, abundance $$39.89\%). $$Use the formula $$	ext{Atomic mass} = (	ext{fractional abundance}_1 	imes 	ext{mass}_1) + (	ext{fractional abundance}_2 	imes 	ext{mass}_2). $$Which value is closest to the correct answer?

Accepted Answer

$$69.72$$ amu

Question 10

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 11

A certain isotope of carbon is represented as $$^{14}\mathrm{C}. $$How many neutrons does this isotope have?

Accepted Answer

8

Question 12

Which of the following best describes the arrangement of electrons in Rutherford’s nuclear model of the atom?

Accepted Answer

Electrons are distributed through a large region of mostly empty space around a dense nucleus.

Question 13

Which of the following elements is a metalloid and is widely used in the electronics industry due to its semiconductor properties?

Accepted Answer

Silicon (Si)

Question 14

Which of the following is the correct symbol notation for an isotope of neon with 10 protons and 12 neutrons?

Accepted Answer

$$^{22}\mathrm{Ne}$$

Question 15

Which of the following best explains why metals are good conductors of electricity?

Accepted Answer

Metals have loosely held valence electrons that can move freely.

Question 16

A magnesium atom loses two electrons to form an ion. What is the symbol and charge of this ion?

Accepted Answer

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

Question 17

Which of the following is a real-world application of radioactive isotopes in medicine?

Accepted Answer

Technetium-99 is used to image internal organs and detect infection.

Question 18

Which of the following best describes the periodic law as observed by Mendeleev?

Accepted Answer

The properties of elements recur in a regular pattern when arranged by increasing atomic mass.

Question 19

If an atom has 17 protons, 18 neutrons, and 17 electrons, what is its isotope symbol?

Accepted Answer

$$^{35}\mathrm{Cl}$$

Question 20

Which of the following best explains why lightning occurs during an electrical storm?

Accepted Answer

Lightning is the result of a quick rebalancing of charge between negatively charged clouds and positively charged ground.

Atoms and Elements: Foundations of Chemistry

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