Q: An atom of chlorine has two naturally occurring isotopes: Cl-35 (mass 34.97 amu, abundance 75.77%) and Cl-37 (mass 36.97 amu, abundance 24.23%). What is the atomic mass of chlorine?

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

Question 1

Which statement best describes the relationship between atoms and elements?

Accepted Answer

Atoms are the smallest identifiable unit of an element, and elements are substances that cannot be broken down into simpler substances.

Question 2

If every atom in a small pebble were enlarged to the size of the pebble itself, how large would the pebble become?

Accepted Answer

Larger than Mount Everest.

Question 3

How many different elements are naturally occurring in nature, according to the study materials?

Accepted Answer

About 91

Question 4

Which of the following is TRUE regarding synthetic elements?

Accepted Answer

Scientists have succeeded in making about 20 synthetic elements.

Question 5

Why is the exact number of naturally occurring elements considered controversial?

Accepted Answer

Because some elements previously considered only synthetic may actually occur in nature in very small quantities.

Question 6

Which ancient philosophers first theorized that matter was made of tiny, indestructible particles called 'atomos'?

Accepted Answer

Democritus and Leucippus

Question 7

According to Dalton’s atomic theory, which of the following is NOT one of its three main parts?

Accepted Answer

Atoms can be divided into smaller particles during chemical reactions.

Question 8

Which experiment led to the rejection of the plum-pudding model of the atom?

Accepted Answer

Rutherford’s gold foil experiment

Question 9

What was the key observation from Rutherford’s gold foil experiment that contradicted the plum-pudding model?

Accepted Answer

Some alpha particles were deflected at sharp angles.

Question 10

According to Rutherford’s nuclear theory, where is most of the atom’s mass and positive charge located?

Accepted Answer

In the nucleus

Question 11

Which subatomic particle has a negligible mass compared to the others?

Accepted Answer

Electron

Question 12

What is the electrical charge of a neutron?

Accepted Answer

0

Question 13

Which of the following best explains why matter is usually charge-neutral?

Accepted Answer

Matter contains equal numbers of positive and negative charges that cancel each other.

Question 14

What is the atomic number (Z) of an element defined as?

Accepted Answer

The number of protons in the nucleus

Question 15

Which of the following elements is NOT an alkali metal, even though it is in Group 1A?

Accepted Answer

Hydrogen

Question 16

Which property is NOT characteristic of metals?

Accepted Answer

Tend to gain electrons in chemical reactions

Question 17

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 18

What is the charge of an ion with 12 protons and 10 electrons?

Accepted Answer

$$12 - 10 = 2+$$

Question 19

An atom of chlorine has two naturally occurring isotopes: Cl-35 (mass 34.97 amu, abundance 75.77%) and Cl-37 (mass 36.97 amu, abundance 24.23%). What is the atomic mass of chlorine?

Accepted Answer

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

Question 20

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.

Atoms and Elements: Foundations of Chemistry

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