Question 1

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

Accepted Answer

Oxygen, carbon, hydrogen, and nitrogen

Question 2

Which statement best describes a trace element?

Accepted Answer

An element required by an organism in minute quantities

Question 3

If an atom has 8 protons, 8 neutrons, and 8 electrons, what is its mass number?

Accepted Answer

$$16$$

Question 4

Which of the following best explains why isotopes of an element have different mass numbers?

Accepted Answer

They have different numbers of neutrons

Question 5

What is the maximum number of electrons that can occupy the second electron shell of an atom?

Accepted Answer

$$8$$

Question 6

Which type of chemical bond involves the sharing of electron pairs between atoms?

Accepted Answer

Covalent bond

Question 7

A sodium atom transfers an electron to a chlorine atom, forming NaCl. What type of bond is formed?

Accepted Answer

Ionic bond

Question 8

Which of the following is a consequence of the unequal sharing of electrons in a polar covalent bond?

Accepted Answer

The molecule has partial positive and negative charges

Question 9

Which statement about hydrogen bonds is correct?

Accepted Answer

They are weak bonds formed between a hydrogen atom and an electronegative atom

Question 10

What is the main reason why water molecules are able to form hydrogen bonds with each other?

Accepted Answer

Water is a polar molecule with partial charges

Question 11

Which of the following best describes the role of valence electrons in chemical bonding?

Accepted Answer

Valence electrons are involved in forming chemical bonds between atoms

Question 12

Which equation correctly represents the formation of water from hydrogen and oxygen?

Accepted Answer

$$2H_2 + O_2$ \rightarrow 2H_2O$$

Question 13

Which of the following is true about chemical reactions?

Accepted Answer

They involve the making and breaking of chemical bonds

Question 14

A radioactive isotope decays and emits particles and energy. Which of the following is a potential biological effect?

Accepted Answer

It can damage molecules within living cells

Question 15

Which of the following best explains why noble gases are chemically inert?

Accepted Answer

They have full valence electron shells

Question 16

Which of the following is a real-world example of a covalent bond?

Accepted Answer

The bond between two hydrogen atoms in a $$H_2$$ molecule

Question 17

Which of the following statements about potential energy in electrons is correct?

Accepted Answer

Electrons in higher energy shells have more potential energy

Question 18

Which of the following best describes the difference between a molecule and a compound?

Accepted Answer

A molecule consists of two or more atoms held together by covalent bonds, while a compound consists of two or more different elements

Question 19

Which of the following is an example of a chemical reaction important in biology?

Accepted Answer

Photosynthesis: $$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2$$

Question 20

Which of the following is true about weak chemical bonds in biological systems?

Accepted Answer

They help maintain the shape of large molecules

Chapter 2: The Chemical Context of Life – Study Notes

Study Guide - Practice Questions