$$\text{Mass Number} = \text{Number of Protons} + \text{Number of Neutrons}$$

Question 1

Which of the following best describes a chemical element?

Accepted Answer

A pure substance made of only one type of atom.

Question 2

Which subatomic particle determines the atomic number of an element?

Accepted Answer

Proton

Question 3

Given an oxygen atom with a mass number of 16 and an atomic number of 8, how many neutrons does it have?

Accepted Answer

$$8$$

Question 4

Which group of elements makes up approximately 97% of the mass of most living organisms?

Accepted Answer

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur

Question 5

What is the correct formula for calculating the mass number of an atom?

Accepted Answer

$$	ext{Mass Number} = 	ext{Number of Protons} + 	ext{Number of Neutrons}$$

Question 6

If the first energy shell of an atom holds up to 2 electrons, how many electrons can the second energy shell hold?

Accepted Answer

$$8$$

Question 7

Which statement about isotopes is TRUE?

Accepted Answer

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

Question 8

A radioactive isotope has a half-life of 5,730 years. How many years must pass for a sample to decay to $$\frac{1}{4} of $$its original amount?

Accepted Answer

$$11,460$$

Question 9

Which of the following is NOT a use of radioactive isotopes?

Accepted Answer

Increasing the number of valence electrons in atoms.

Question 10

According to the octet rule, why is neon (Ne) chemically unreactive?

Accepted Answer

It has a full valence shell of electrons.

Question 11

How many electrons does an oxygen atom need to fulfill the octet rule?

Accepted Answer

$$2$$

Question 12

Which of the following statements about electron energy shells is TRUE?

Accepted Answer

Shells closer to the nucleus contain electrons with lower energy.

Question 13

Which of the following is the correct chemical formula for glucose?

Accepted Answer

$$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$$

Question 14

Which of the following best explains why carbon is essential for life?

Accepted Answer

It can form four covalent bonds, allowing for complex molecules.

Question 15

What is the relationship between atomic number and the number of protons in an atom?

Accepted Answer

Atomic number equals the number of protons.

Question 16

Which of the following elements is NOT one of the CHNOPS elements?

Accepted Answer

Calcium

Question 17

If an atom has 15 protons, 16 neutrons, and 15 electrons, what is its atomic mass?

Accepted Answer

$$31$$

Question 18

Which of the following statements about ions is correct?

Accepted Answer

Anions have more electrons than protons.

Question 19

How are carbon-13 and carbon-14 different from carbon-12?

Accepted Answer

They have more neutrons.

Question 20

Which of the following is a trace element required in small amounts for life?

Accepted Answer

Iron

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