Question 1

Which of the following statements best explains why oxygen atoms can form two covalent bonds?

Accepted Answer

Oxygen has space for two more electrons in its valence shell, allowing it to form two covalent bonds.

Question 2

A compound is defined as:

Accepted Answer

A substance consisting of two or more elements in a fixed ratio.

Question 3

Which element makes up the largest percentage of human body mass?

Accepted Answer

Oxygen

Question 4

What is the atomic number of an element, and how is it determined?

Accepted Answer

The number of protons in the nucleus.

Question 5

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 6

If a carbon atom has 6 protons and 8 neutrons, what is its mass number?

Accepted Answer

$$14$$

Question 7

Which of the following is true about ionic bonds?

Accepted Answer

They result from the attraction between oppositely charged ions.

Question 8

What is the main difference between a polar covalent bond and a nonpolar covalent bond?

Accepted Answer

In polar covalent bonds, electrons are shared unequally due to differences in electronegativity.

Question 9

Which of the following best describes a hydrogen bond?

Accepted Answer

A weak attraction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Question 10

Which of the following molecules contains a double covalent bond?

Accepted Answer

O$$_2$$

Question 11

A sodium atom ($$Na) $$transfers an electron to a chlorine atom ($$Cl) to $$form sodium chloride ($$NaCl). $$What type of bond is formed?

Accepted Answer

Ionic bond

Question 12

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

Accepted Answer

They have a full valence shell of electrons.

Question 13

Which of the following is a correct statement about the relationship between atomic number and chemical properties?

Accepted Answer

The atomic number determines the number of protons, which defines the element and influences its chemical behavior.

Question 14

Which of the following elements is present in the human body at less than 0.01% of body mass?

Accepted Answer

Boron

Question 15

A radioactive isotope differs from a stable isotope in that it:

Accepted Answer

Decays spontaneously, giving off particles and energy.

Question 16

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

Accepted Answer

Valence electrons are shared or transferred during chemical bonding, determining the atom's chemical behavior.

Question 17

Which of the following is the correct molecular formula for formic acid?

Accepted Answer

$$CH_2O_2$$

Question 18

If an atom has 11 protons, 12 neutrons, and 11 electrons, what is its atomic mass?

Accepted Answer

$$23$$

Question 19

Which of the following best explains why water molecules are polar?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing unequal sharing of electrons.

Question 20

A molecule of ammonia ($$NH_3) $$can form hydrogen bonds with water molecules. Which property of ammonia allows this interaction?

Accepted Answer

Ammonia contains hydrogen atoms covalently bonded to a highly electronegative atom (nitrogen).

Chapter 2: The Chemical Context of Life – Study Notes

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