Question 1

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

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 of the following statements about isotopes is TRUE?

Accepted Answer

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

Question 4

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

$$11,460$$ years

Question 5

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

Accepted Answer

Its valence shell is full.

Question 6

According to the octet rule, how many electrons does an oxygen atom need to gain to fill its valence shell?

Accepted Answer

$$2$$

Question 7

Which of the following is a correct statement about electron shells?

Accepted Answer

Valence electrons are found in the outermost shell.

Question 8

If an atom has $$6$$ protons, $$8$$ neutrons, and $$6$$ electrons, what is its atomic mass?

Accepted Answer

$$14$$

Question 9

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

Accepted Answer

Determining the age of fossils using carbon dating.

Question 10

How are carbon-13 and nitrogen-15 isotopes different from the more abundant carbon-12 and nitrogen-14 isotopes?

Accepted Answer

Each has one extra neutron.

Question 11

Which of the following best describes the relationship between atomic number and the identity of an element?

Accepted Answer

The atomic number is equal to the number of protons.

Question 12

Which of the following statements about the periodic table is correct?

Accepted Answer

It arranges elements by increasing atomic number.

Question 13

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

Accepted Answer

$$8$$

Question 14

Which of the following is a property of a radioactive isotope?

Accepted Answer

It emits energy as it decays.

Question 15

Which of the following best explains why atoms are more stable when their valence shells are full?

Accepted Answer

They are less likely to react with other atoms.

Question 16

If a carbon atom has $$6$$ protons and $$7$$ neutrons, what is its isotope name?

Accepted Answer

Carbon-13

Question 17

Which of the following is NOT a use of radioactive isotopes in biology or medicine?

Accepted Answer

Increasing the atomic number of an element

Question 18

Which of the following statements about the mass number of an atom is correct?

Accepted Answer

It is equal to the sum of protons and neutrons.

Question 19

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

Accepted Answer

Iron

Question 20

If the atomic number of an element is $$12$$ and its mass number is $$24$$, how many neutrons does it have?

Accepted Answer

$$12$$

Atoms, Elements, and the Chemical Basis of Life: General Biology Study Notes

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