Question 1

Which statement best explains why electrons in the same shell repel each other?

Accepted Answer

Because electrons are negatively charged and like charges repel according to Coulomb's law: $F = k \frac{q_1 q_2}{r^2}$.

Question 2

An atom of oxygen has 8 electrons. How are these electrons distributed among its shells?

Accepted Answer

2 electrons in the first shell, 6 electrons in the second shell.

Question 3

Which element is the most abundant in the human body by mass, and what is its approximate percentage?

Accepted Answer

Oxygen, 65%

Question 4

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

Accepted Answer

8

Question 5

Which of the following best describes an emergent property in chemistry?

Accepted Answer

A property that arises only when atoms combine to form compounds, and is not present in the individual elements.

Question 6

Sodium (Na) is a soft, silvery metal that explodes in water, while chlorine (Cl) is a toxic yellow gas. When they react, they form sodium chloride (NaCl), which is table salt. What does this illustrate?

Accepted Answer

The concept of emergent properties, where the compound has characteristics different from its constituent elements.

Question 7

Which of the following statements about valence electrons is correct?

Accepted Answer

Valence electrons are the electrons in the outermost shell and determine chemical reactivity.

Question 8

What type of chemical bond is formed when one atom completely transfers an electron to another atom?

Accepted Answer

Ionic bond

Question 9

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of unpaired valence electrons between two atoms.

Question 10

Which formula correctly represents the relationship between the force of attraction or repulsion between two charged particles?

Accepted Answer

$F = k \frac{q_1 q_2}{r^2}$

Question 11

If the electronegativity difference between two atoms is greater than 2, what type of bond will most likely form?

Accepted Answer

Ionic bond

Question 12

Which of the following molecules contains a polar covalent bond?

Accepted Answer

H$_2$O

Question 13

What is the main reason water (H$_2$O) molecules can form hydrogen bonds with each other?

Accepted Answer

Because oxygen is highly electronegative, creating partial charges on the molecule.

Question 14

Which of the following best describes a nonpolar covalent bond?

Accepted Answer

Bonding electrons are shared equally between two atoms, resulting in no charges on atoms.

Question 15

Which of the following is a trace element in the human body, making up less than 0.01% of body mass?

Accepted Answer

Iron

Question 16

A molecule of methane (CH$_4$) is formed when carbon shares electrons with four hydrogen atoms. What type of bond is present between carbon and hydrogen?

Accepted Answer

Nonpolar covalent bond

Question 17

Which of the following is true about the octet rule?

Accepted Answer

Atoms are most stable when their outermost shell contains 8 electrons.

Question 18

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have complete valence shells, making them energetically stable.

Question 19

Which of the following is a correct representation of a double covalent bond?

Accepted Answer

O=O

Question 20

A patient is found to have a deficiency in magnesium (Mg), which is about 0.1% of body mass. Which of the following symptoms might be expected based on magnesium's role in the body?

Accepted Answer

Muscle cramps and irregular heartbeat due to its role in nerve and muscle function.

Atomic Structure, Electron Configuration, and Chemical Bonds in Biology

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