Question 1

According to Dalton’s atomic theory, which statement best explains why water (H$$_2O) $$and hydrogen peroxide (H$$_2O$_2) $$are different substances even though both are composed of hydrogen and oxygen?

Accepted Answer

Atoms of different elements combine in simple, whole-number ratios to form different compounds.

Question 2

Which experimental result led Rutherford to propose the nuclear model of the atom?

Accepted Answer

Most alpha particles passed straight through the gold foil, but a few were deflected at large angles.

Question 3

Which of the following best describes Thomson’s plum pudding model of the atom?

Accepted Answer

A sphere of positive charge with electrons scattered throughout.

Question 4

A neutral atom of sodium (Na) has an atomic number of 11 and a mass number of 23. How many protons, neutrons, and electrons does it have?

Accepted Answer

11 protons, 12 neutrons, 11 electrons

Question 5

Which of the following statements about electrical charge is correct?

Accepted Answer

Positive and negative charges attract and cancel each other, resulting in a neutral charge.

Question 6

Given the isotope notation $$^{206}_{82}\mathrm{Pb}$$, how many neutrons are present in this isotope of lead?

Accepted Answer

$$206 - 82 = 124$$ neutrons

Question 7

Which of the following ions has 20 protons and 18 electrons? Write the correct symbol.

Accepted Answer

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

Question 8

Which property is NOT typical of metals?

Accepted Answer

Tends to gain electrons in chemical reactions

Question 9

A neutral atom has 17 protons and 18 neutrons. What is its atomic number, mass number, and element symbol?

Accepted Answer

Atomic number = 17, mass number = 35, symbol = Cl

Question 10

Which of the following best explains why isotopes of the same element have nearly identical chemical properties?

Accepted Answer

They have the same number of protons and electrons.

Question 11

Which element is represented by the symbol 'Fe' and what is its atomic number?

Accepted Answer

Iron, atomic number 26

Question 12

Which of the following statements about the periodic table is FALSE?

Accepted Answer

Elements are arranged in order of increasing atomic mass.

Question 13

A neutral atom of magnesium (Mg) has 12 protons. If it loses two electrons, what is the charge and symbol of the resulting ion?

Accepted Answer

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

Question 14

Which of the following is a property of metalloids?

Accepted Answer

They have intermediate electrical conductivity that can be controlled.

Question 15

Which of the following best describes the difference between a cation and an anion?

Accepted Answer

A cation is positively charged due to loss of electrons; an anion is negatively charged due to gain of electrons.

Question 16

Which of the following pairs are isotopes of the same element?

Accepted Answer

$$^{31}_{16}\mathrm{X}$$ and $$^{32}_{16}\mathrm{X}$$

Question 17

Which of the following best explains why most alpha particles passed straight through the gold foil in Rutherford’s experiment?

Accepted Answer

The gold atoms are mostly empty space.

Question 18

If an atom has 15 protons, 16 neutrons, and 18 electrons, what is the symbol and charge of the ion?

Accepted Answer

$$\mathrm{P}^{3-}$$

Question 19

Which of the following is a correct statement about the size of the atom and its nucleus?

Accepted Answer

The nucleus is about 10,000 times smaller in diameter than the atom.

Question 20

Which of the following is the correct formula for calculating the number of neutrons in an atom?

Accepted Answer

$$N = A - Z$$

Atoms, Elements, and the Structure of Matter: Foundations of Atomic Theory

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