Q: Calculate the average atomic mass of chlorine given the following data: 75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu).

$$(0.7577 \times 34.97) + (0.2423 \times 36.97) = 35.45$$ amu

Question 1

Which statement best summarizes Dalton’s atomic theory as it relates to the composition of water (H$$_2O$$)?

Accepted Answer

Water is composed of hydrogen and oxygen atoms that are chemically bonded in a 2:1 ratio, and each atom retains its identity during chemical reactions.

Question 2

Rutherford’s gold foil experiment led to which major revision of the atomic model?

Accepted Answer

Atoms have a small, dense, positively charged nucleus where most of the mass is concentrated.

Question 3

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

Accepted Answer

Most of the atom is empty space, allowing alpha particles to pass through without deflection.

Question 4

Which subatomic particle determines the identity of an element?

Accepted Answer

Proton

Question 5

A neutral atom of potassium (K) has an atomic number of 19. How many electrons does it contain?

Accepted Answer

19

Question 6

Which of the following elements is a metalloid?

Accepted Answer

Silicon (Si)

Question 7

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

Accepted Answer

Noble gases (Group 8A)

Question 8

A magnesium ion has 10 electrons. What is its charge?

Accepted Answer

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

Question 9

Which of the following is the correct isotope symbol for a boron atom with 5 protons and 5 neutrons?

Accepted Answer

$$^{10}\mathrm{B}$$

Question 10

Which of the following best describes the trend in reactivity for alkali metals (Group 1A) as you move down the group?

Accepted Answer

Reactivity increases as you move down the group.

Question 11

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 12

Calculate the average atomic mass of chlorine given the following data: 75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu).

Accepted Answer

$$(0.7577 	imes 34.97) + (0.2423 	imes 36.97) = 35.45$$ amu

Question 13

Which of the following ions is an anion?

Accepted Answer

$$\mathrm{Cl$$^{-}$$}$$

Question 14

Which property is NOT characteristic of metals?

Accepted Answer

Poor conductivity of heat and electricity

Question 15

Which element is most likely to form a $$2-$$ ion?

Accepted Answer

Oxygen (O)

Question 16

A sulfur ion has 18 electrons. What is its charge?

Accepted Answer

$$\mathrm{S$$^{2-}$$}$$

Question 17

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

Accepted Answer

Electrons are dispersed in a cloud around a small, dense nucleus.

Question 18

Which of the following elements is a halogen?

Accepted Answer

Bromine (Br)

Question 19

Which of the following best explains why atoms are electrically neutral?

Accepted Answer

The number of protons equals the number of electrons.

Question 20

Which of the following is the correct symbol for a gold atom?

Accepted Answer

Au

Atoms and Elements: Structured Study Notes for Introductory Chemistry

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