Question 1

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

Accepted Answer

An element is a pure substance consisting of only one type of atom, while a compound consists of two or more different elements chemically bonded together.

Question 2

Which subatomic particle determines the atomic number of an element?

Accepted Answer

Proton

Question 3

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

Accepted Answer

$18$

Question 4

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 5

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

Accepted Answer

$2$

Question 6

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

Accepted Answer

Covalent bond

Question 7

A sodium atom ($Na$) loses one electron to become $Na^+$. What type of ion is $Na^+$?

Accepted Answer

Cation

Question 8

Which of the following molecules is a compound?

Accepted Answer

$H_2O$

Question 9

Which element is most abundant in the human body (excluding water)?

Accepted Answer

Oxygen

Question 10

What is the main reason atoms form chemical bonds?

Accepted Answer

To achieve a full outer electron shell (valence shell)

Question 11

Which of the following best describes a polar covalent bond?

Accepted Answer

Electrons are shared unequally, resulting in partial charges on the atoms.

Question 12

Which of the following is a trace element required by living organisms in very small amounts?

Accepted Answer

Iron

Question 13

Given the electronegativity values: $O = 3.5$, $H = 2.1$, what type of bond is formed between oxygen and hydrogen in water ($H_2O$)?

Accepted Answer

Polar covalent bond

Question 14

Which of the following best explains why $NaCl$ (table salt) forms an ionic bond?

Accepted Answer

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

Question 15

Which of the following is the correct formula for glucose, a compound found in living organisms?

Accepted Answer

$C_6H_{12}O_6$

Question 16

If an atom has a full valence shell, how is it likely to behave?

Accepted Answer

It is chemically inert.

Question 17

Which of the following best describes a hydrogen bond?

Accepted Answer

A bond formed by the attraction between a hydrogen atom with a partial positive charge and another atom with a partial negative charge.

Question 18

Which of the following is NOT a molecule?

Accepted Answer

$Na^+$

Question 19

A radioactive isotope of carbon ($^{14}C$) is used in medical imaging. What makes $^{14}C$ radioactive?

Accepted Answer

It has an unstable number of neutrons, causing it to decay and emit energy.

Question 20

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

Accepted Answer

Oxygen is more electronegative than hydrogen, causing an unequal sharing of electrons and partial charges.

Atomic Structure, Elements, and Chemical Bonds: Foundations of General Biology

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