Q: What is the atomic mass of an element with the following isotopic composition: 75% isotope A (mass = 10 amu), 25% isotope B (mass = 12 amu)?

$$(0.75 \times 10) + (0.25 \times 12) = 7.5 + 3 = 10.5$$ amu

Q: A sample of Floridium contains 46.700% Fl-315 (315.00 amu), 31.000% Fl-317 (317.00 amu), and 22.300% Fl-320 (320.00 amu). What is the atomic mass of Floridium?

$$(0.46700 \times 315.00) + (0.31000 \times 317.00) + (0.22300 \times 320.00) = 146.105 + 98.27 + 71.36 = 315.74$$ amu

Question 1

Which experiment led to the discovery that atoms have a small, dense, positively charged nucleus?

Accepted Answer

Ernest Rutherford's gold foil experiment

Question 2

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

Accepted Answer

Atoms can be divided into smaller particles by chemical processes.

Question 3

A neutral atom of sodium has an atomic number of 11 and a mass number of 23. How many neutrons does it have?

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 4

Which property is characteristic of metals but NOT of nonmetals?

Accepted Answer

Malleable and ductile

Question 5

Which element is a noble gas in the third period of the periodic table?

Accepted Answer

Neon (Ne)

Question 6

What is the atomic mass of an element with the following isotopic composition: 75% isotope A (mass = 10 amu), 25% isotope B (mass = 12 amu)?

Accepted Answer

$$(0.75 	imes 10) + (0.25 	imes 12) = 7.5 + 3 = 10.5$$ amu

Question 7

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 8

Which group on the periodic table contains elements that are very reactive and have one valence electron?

Accepted Answer

Group IA (alkali metals)

Question 9

A chlorine atom gains one electron to form an ion. What is the correct formula for this ion?

Accepted Answer

$$\mathrm{Cl}^-$$

Question 10

Which scientist is credited with discovering the electron?

Accepted Answer

J.J. Thomson

Question 11

Which of the following is a metalloid and is commonly used in the electronics industry due to its semiconducting properties?

Accepted Answer

Silicon (Si)

Question 12

Which law did Dalton use to support his atomic theory, stating that a compound always contains the same elements in the same proportion by mass?

Accepted Answer

Law of Definite Composition

Question 13

Which of the following elements is most abundant in the human body?

Accepted Answer

Oxygen

Question 14

Which of the following ions is formed when magnesium reacts to achieve a noble gas configuration?

Accepted Answer

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

Question 15

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

Accepted Answer

Elements in the same group have similar chemical properties.

Question 16

A sample of Floridium contains 46.700% Fl-315 (315.00 amu), 31.000% Fl-317 (317.00 amu), and 22.300% Fl-320 (320.00 amu). What is the atomic mass of Floridium?

Accepted Answer

$$(0.46700 	imes 315.00) + (0.31000 	imes 317.00) + (0.22300 	imes 320.00) = 146.105 + 98.27 + 71.36 = 315.74$$ amu

Question 17

Which of the following best describes the charge and location of a neutron in an atom?

Accepted Answer

No charge, inside the nucleus

Question 18

Which of the following elements is a transition metal?

Accepted Answer

Iron (Fe)

Question 19

Which of the following is the correct atomic notation for a neutral atom of chlorine-37?

Accepted Answer

$$^{37}_{17}\mathrm{Cl}$$

Atoms and Elements: Structure, History, and the Periodic Table

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