Question 1

Which of the following statements best describes a compound?

Accepted Answer

A molecule that contains two or more different elements bonded together in a fixed ratio.

Question 2

Which four elements make up approximately 96% of living matter?

Accepted Answer

Oxygen, Carbon, Hydrogen, Nitrogen

Question 3

An atom of phosphorus has an atomic number of 15 and an atomic mass of 30.97. How many neutrons does a typical atom of phosphorus have?

Accepted Answer

$$30.97 - 15 = 15.97$$, so approximately 16 neutrons

Question 4

Which of the following best explains why electrons remain in orbit around the nucleus of an atom?

Accepted Answer

Because of the attraction between the negatively charged electrons and the positively charged protons in the nucleus.

Question 5

Which of the following is the correct definition of a valence electron?

Accepted Answer

An electron located in the outermost shell of an atom, involved in chemical bonding.

Question 6

A neutral atom of nitrogen has an atomic number of 7. How many electrons does it have, and how many are in its outermost shell?

Accepted Answer

7 electrons total, 5 in the outermost shell

Question 7

Which of the following best describes the difference between atomic number and atomic mass?

Accepted Answer

Atomic number is the number of protons; atomic mass is the sum of protons and neutrons.

Question 8

Which of the following best explains why radioactive isotopes are useful in medicine?

Accepted Answer

They emit radiation that can be detected, allowing doctors to trace the movement of substances in the body.

Question 9

If an atom has 6 protons, 6 neutrons, and 6 electrons, what is its atomic number and atomic mass?

Accepted Answer

Atomic number: 6; Atomic mass: $$6 + 6 = 12$$

Question 10

Which of the following statements about energy levels (shells) in atoms is correct?

Accepted Answer

Electrons in the outermost shell have the highest energy.

Question 11

A sodium atom has 11 electrons. How many electrons does it need to lose to achieve a full outer shell, and what will its resulting charge be?

Accepted Answer

It needs to lose 1 electron; resulting charge will be $$+1$$

Question 12

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 13

Which type of bond is the strongest in biological systems?

Accepted Answer

Covalent bond

Question 14

How many covalent bonds is a carbon atom likely to form, based on its number of valence electrons?

Accepted Answer

4

Question 15

Which of the following best explains the octet rule in chemistry?

Accepted Answer

Atoms tend to gain, lose, or share electrons to achieve a full outer shell of 8 electrons.

Question 16

Which of the following scenarios best illustrates the concept of a molecule?

Accepted Answer

Two hydrogen atoms and one oxygen atom bonded together to form $$\mathrm{H_2O}.$$

Question 17

Which of the following is a correct statement about protons, neutrons, and electrons?

Accepted Answer

Protons and neutrons are found in the nucleus, while electrons orbit the nucleus.

Question 18

A patient is given a radioactive isotope for a PET scan. Which property of the isotope allows doctors to track its movement in the body?

Accepted Answer

It emits detectable radiation as it decays.

Question 19

Which of the following best describes the process that occurs when an electron moves from a lower energy shell to a higher energy shell?

Accepted Answer

The electron absorbs a specific amount of energy.

Question 20

Which of the following is the correct formula for calculating the atomic mass of an atom?

Accepted Answer

$$	ext{Atomic mass} = 	ext{Number of protons} + 	ext{Number of neutrons}$$

Atoms, Elements, and Chemical Bonds: Foundations of General Biology

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