Question 1

Which of the following statements best explains why helium, neon, and argon are chemically unreactive under normal conditions?

Accepted Answer

They have full outer electron shells, making them stable and unlikely to form chemical bonds.

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 have?

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 3

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with the same number of protons but different numbers of neutrons.

Question 4

A radioactive isotope of phosphorus, $$^{32}P$$, undergoes decay in which a neutron becomes a proton and an electron. What is the new atomic number after this decay?

Accepted Answer

The atomic number increases by 1.

Question 5

Which of the following best explains why water ($$H_2O) is a $$polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, so shared electrons are pulled closer to the oxygen atom, creating partial charges.

Question 6

Which type of bond is formed when one atom donates an electron to another atom, resulting in oppositely charged ions that attract each other?

Accepted Answer

Ionic bond

Question 7

A carbon atom has 6 protons, 6 electrons, and 8 neutrons. What is its mass number?

Accepted Answer

$$6 + 8 = 14$$

Question 8

Which of the following is NOT a compound?

Accepted Answer

$$O_2$$

Question 9

If an atom has a vacancy in its outermost electron shell, what is most likely to happen?

Accepted Answer

It will interact with other atoms to fill its outer shell, forming chemical bonds.

Question 10

Which of the following best describes a hydrogen bond?

Accepted Answer

A weak attraction between a slightly positive hydrogen atom in one polar molecule and a slightly negative atom in another polar molecule.

Question 11

Which of the following statements about ions is correct?

Accepted Answer

An ion is an atom or molecule with a different number of protons and electrons, resulting in a net charge.

Question 12

Which of the following best explains why sodium and chlorine form an ionic bond in table salt ($$NaCl$$)?

Accepted Answer

Sodium donates an electron to chlorine, resulting in oppositely charged ions that attract each other.

Question 13

Which of the following is a correct statement about valence electrons?

Accepted Answer

Valence electrons are the electrons in the outermost shell of an atom and are involved in forming chemical bonds.

Question 14

Which of the following scenarios would most likely result in the formation of a nonpolar covalent bond?

Accepted Answer

Two atoms with identical or very similar electronegativities share electrons equally.

Question 15

A patient is injected with a radioactive isotope that has a short half-life. What is the most likely reason for using an isotope with a short half-life in medical diagnosis?

Accepted Answer

It decays quickly, minimizing radiation exposure to the patient.

Question 16

Which of the following best describes the relationship between atomic number and the identity of an element?

Accepted Answer

The atomic number is equal to the number of protons in the nucleus, which determines the element's identity.

Question 17

Which of the following best explains why isotopes of the same element have nearly identical chemical properties?

Accepted Answer

They have the same number of electrons and protons, so their chemical behavior is the same.

Question 18

Which of the following is the correct electron configuration for a neutral atom of carbon (atomic number 6)?

Accepted Answer

2 electrons in the first shell, 4 electrons in the second shell

Question 19

Which of the following best describes a polar covalent bond?

Accepted Answer

A bond in which electrons are shared unequally between atoms with different electronegativities.

Question 20

A molecule of methane ($$CH_4) is $$formed when carbon bonds with four hydrogen atoms. What type of bond is formed between carbon and hydrogen in methane?

Accepted Answer

Nonpolar covalent bond

Chapter 2 first half

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