Question 1

Which of the following elements is NOT one of the six most abundant elements in living organisms (CHNOPS)?

Accepted Answer

Calcium

Question 2

An atom of oxygen has an atomic number of 8 and a mass number of 16. How many neutrons does it have?

Accepted Answer

$$8$$

Question 3

Which statement best describes isotopes of an element?

Accepted Answer

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

Question 4

A radioactive isotope has a half-life of $$5,000$$ years. If you start with a $$100 g $$sample, how much will remain after $$10,000$$ years?

Accepted Answer

$$25 g$$

Question 5

Which of the following best explains why neon (Ne) is chemically unreactive?

Accepted Answer

Its valence shell is full.

Question 6

How many electrons are needed for an oxygen atom to fill its valence shell according to the octet rule?

Accepted Answer

$$2$$

Question 7

Which of the following is TRUE about electron energy shells?

Accepted Answer

Shells closer to the nucleus are lower in energy.

Question 8

What is the atomic number of an atom with $$6$$ protons, $$6$$ neutrons, and $$6$$ electrons?

Accepted Answer

$$6$$

Question 9

Which of the following is a correct statement about cations and anions?

Accepted Answer

Cations have more protons than electrons.

Question 10

A sample contains a mixture of carbon-12, carbon-13, and carbon-14. Which isotope is most abundant in nature?

Accepted Answer

Carbon-12

Question 11

Which of the following is a real-world application of radioactive isotopes?

Accepted Answer

Dating fossils to determine their age

Question 12

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

Accepted Answer

$$31$$

Question 13

Which of the following best describes the relationship between atomic number and the periodic table?

Accepted Answer

Elements are arranged in order of increasing atomic number.

Question 14

Which of the following statements about valence electrons is correct?

Accepted Answer

Valence electrons are found in the outermost energy shell.

Question 15

A nitrogen atom has an atomic number of $$7$$ and a mass number of $$15. $$How many neutrons does it have?

Accepted Answer

$$8$$

Question 16

Which of the following is a property of a chemical element?

Accepted Answer

It is a pure substance made of only one type of atom.

Question 17

Which of the following best explains why atoms form chemical bonds?

Accepted Answer

To achieve a full valence shell and become more stable

Question 18

Which of the following is the correct formula for glucose?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$}$$

Question 19

Which of the following statements about protons is TRUE?

Accepted Answer

They determine the atomic number of an element.

Question 20

A radioactive isotope is used in medical imaging and has a half-life of $$3$$ hours. If a patient is injected with $$80 mg$$, how much remains after $$9$$ hours?

Accepted Answer

$$10 mg$$

Atoms, Elements, and Atomic Structure: General Chemistry Study Notes

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