Q: Calculate the average atomic mass of neon given the following isotopic abundances: $$^{20}Ne (90.48$$%, mass = 19.992 amu), $$^{21}Ne (0.27$$%, mass = 20.994 amu), $$^{22}Ne (9.25$$%, mass = 21.991 amu).

$$(0.9048 \times 19.992) + (0.0027 \times 20.994) + (0.0925 \times 21.991) = 20.18$$ amu

Question 1

Which experiment provided evidence that atoms are mostly empty space with a small, dense, positively charged nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 2

According to Dalton's atomic theory, which statement is correct?

Accepted Answer

Atoms of a given element are identical in mass and properties.

Question 3

A neutral atom of magnesium has an atomic number $$Z = 12$$ and a mass number $$A = 24. $$How many neutrons does it contain?

Accepted Answer

$$12$$

Question 4

Which law states that a chemical compound always contains the same proportion of elements by mass?

Accepted Answer

Law of Definite Proportions

Question 5

A sample of sulfur dioxide ($$SO_2) $$decomposes to $$3.49 g $$oxygen and $$3.50 g $$sulfur. A sample of sulfur trioxide ($$SO_3) $$decomposes to $$6.75 g $$oxygen and $$4.50 g $$sulfur. What is the ratio of the mass of oxygen per gram of sulfur in $$SO_3$$ compared to $$SO_2$$?

Accepted Answer

$$\dfrac{6.75/4.50}{3.49/3.50} = 1.5$$

Question 6

Which of the following is the correct isotope symbol for a silver atom with 60 neutrons?

Accepted Answer

$$^{107}_{47}Ag$$

Question 7

How many electrons are in a $$O^{2-}$$ ion?

Accepted Answer

$$10$$

Question 8

Which element is most chemically similar to chlorine?

Accepted Answer

Fluorine

Question 9

Calculate the average atomic mass of neon given the following isotopic abundances: $$^{20}Ne (90.48$$%, mass = 19.992 amu), $$^{21}Ne (0.27$$%, mass = 20.994 amu), $$^{22}Ne (9.25$$%, mass = 21.991 amu).

Accepted Answer

$$(0.9048 	imes 19.992) + (0.0027 	imes 20.994) + (0.0925 	imes 21.991) = 20.18$$ amu

Question 10

Which of the following statements is consistent with Rutherford's nuclear theory?

Accepted Answer

The nucleus of an atom is small compared to the size of the atom.

Question 11

A neutral atom of potassium ($$K) $$has 19 protons. What is the symbol for a potassium ion with a $$+1$$ charge?

Accepted Answer

$$K^{+}$$

Question 12

Which experiment determined the charge of a single electron?

Accepted Answer

Millikan's oil drop experiment

Question 13

Which of the following is a main-group element?

Accepted Answer

Calcium

Question 14

What is the charge on an ion formed when a neutral sulfur atom gains two electrons?

Accepted Answer

$$2-$$

Question 15

Which law is illustrated when two elements form more than one compound, and the masses of one element that combine with a fixed mass of the other are in a ratio of small whole numbers?

Accepted Answer

Law of Multiple Proportions

Question 16

How many atoms are in $$2.00$$ moles of carbon? ($$N_A = 6.022 	imes 10$$^{23}$$ mol$$^{-1}$$)

Accepted Answer

$$1.20 	imes 10$$^{24}$$

Question 17

Which element is represented by the isotope symbol $$^{52}_{24}Cr$$?

Accepted Answer

Chromium

Question 18

Which of the following best describes the periodic law?

Accepted Answer

When elements are arranged in order of increasing atomic number, certain sets of properties recur periodically.

Question 19

A neutral atom of $$^{23}_{11}Na$$ loses one electron. What is the resulting ion's symbol and charge?

Accepted Answer

$$^{23}_{11}Na$$^{+}$$

Question 20

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

Accepted Answer

Atoms can be converted into other elements by chemical reactions.

Atoms and Elements: Foundations of Atomic Theory and the Periodic Table

Guida di studio - Domande di pratica

Study guide - Flashcard