Q: What is the atomic mass of an element with two isotopes: 70% with mass 10 amu and 30% with mass 12 amu?

$$(0.70 \times 10) + (0.30 \times 12) = 10.6$$ amu

Q: Calculate the atomic mass of Floridium given the following isotopic abundances: 46.700% Fl-315 (315.00 amu), 31.000% Fl-317 (317.00 amu), 22.300% Fl-320 (320.00 amu).

$$(0.46700 \times 315.00) + (0.31000 \times 317.00) + (0.22300 \times 320.00) = 316.6$$ amu

Question 1

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

Accepted Answer

Atoms have a small, dense, positively charged nucleus surrounded by mostly empty space.

Question 2

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

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 3

Which of the following is a property of metals?

Accepted Answer

They are malleable and ductile.

Question 4

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

Accepted Answer

Argon (Ar)

Question 5

What is the atomic mass of an element with two isotopes: 70% with mass 10 amu and 30% with mass 12 amu?

Accepted Answer

$$(0.70 	imes 10) + (0.30 	imes 12) = 10.6$$ amu

Question 6

Which scientist is credited with the discovery of the electron?

Accepted Answer

J.J. Thomson

Question 7

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 8

A chlorine atom forms an ion by gaining one electron. What is the correct formula for this ion?

Accepted Answer

$$\mathrm{Cl}^-$$

Question 9

Which of the following elements is a metalloid?

Accepted Answer

Silicon (Si)

Question 10

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 11

Which of the following is the correct atomic notation for a neutral atom of manganese with a mass number of 55?

Accepted Answer

$$^{55}_{25}\mathrm{Mn}$$

Question 12

Which group on the periodic table contains the most reactive nonmetals?

Accepted Answer

Group VIIA (halogens)

Question 13

A sample of carbon contains 99% $$^{12}\mathrm{C}$$, 1% $$^{13}\mathrm{C}$$, and a trace of $$^{14}\mathrm{C}. $$Which isotope is most abundant?

Accepted Answer

$$^{12}\mathrm{C}$$

Question 14

Which of the following best explains why metals tend to form cations?

Accepted Answer

Metals lose electrons from their valence shell, resulting in a positive charge.

Question 15

Which scientist arranged the periodic table by increasing atomic number, leading to the modern periodic law?

Accepted Answer

H.G.J. Moseley

Question 16

Calculate the atomic mass of Floridium given the following isotopic abundances: 46.700% Fl-315 (315.00 amu), 31.000% Fl-317 (317.00 amu), 22.300% Fl-320 (320.00 amu).

Accepted Answer

$$(0.46700 	imes 315.00) + (0.31000 	imes 317.00) + (0.22300 	imes 320.00) = 316.6$$ amu

Question 17

Which of the following is NOT a property of nonmetals?

Accepted Answer

Malleable and ductile

Question 18

Which element is named after a person?

Accepted Answer

Nobelium

Question 19

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

Accepted Answer

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

Question 20

Which of the following best describes the periodic law?

Accepted Answer

The properties of elements repeat in a predictable pattern when arranged by increasing atomic number.

Atoms and Elements: Foundations of Chemistry

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