Q: Which of the following is the correct formula for calculating the mass number of an atom?

$$\text{Mass number} = \text{Number of protons} + \text{Number of neutrons}$$

Question 1

Which of the following best describes the difference between an atom and a molecule?

Accepted Answer

An atom is a single unit of an element, while a molecule is composed of two or more atoms bonded together.

Question 2

Which of the following elements is NOT one of the four most common elements found in living things?

Accepted Answer

Calcium

Question 3

A neutral atom of carbon has an atomic number of 6 and a mass number of 14. How many neutrons does it have?

Accepted Answer

$$14 - 6 = 8$$ neutrons

Question 4

Which statement correctly describes the location and charge of subatomic particles in an atom?

Accepted Answer

Protons and neutrons are in the nucleus; electrons are in orbitals around the nucleus.

Question 5

Which of the following best defines a radioactive isotope?

Accepted Answer

An isotope with an unstable nucleus that emits radiation as it decays.

Question 6

A certain element has an atomic number of 8. Which of the following statements is true for a neutral atom of this element?

Accepted Answer

It has 8 protons and 8 electrons.

Question 7

Which of the following best describes the difference between atomic number and mass number?

Accepted Answer

Atomic number is the number of protons; mass number is the sum of protons and neutrons.

Question 8

Which of the following is a compound?

Accepted Answer

H$$_2O$$

Question 9

A scientist is using a radioactive isotope to trace the movement of a substance in a living organism. Which property of radioactive isotopes makes this possible?

Accepted Answer

They emit detectable radiation as they decay.

Question 10

Which of the following best describes a chemical reaction?

Accepted Answer

A process in which atoms are rearranged to form new substances.

Question 11

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 12

Which of the following 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 13

Which subatomic particle determines the identity of an element?

Accepted Answer

Proton

Question 14

A sample contains two isotopes of chlorine: $$^{35}Cl $$and $$^{37}Cl. $$Both have 17 protons. How many neutrons does $$^{37}Cl $$have?

Accepted Answer

$$37 - 17 = 20$$ neutrons

Question 15

Which of the following best describes a dalton (atomic mass unit, AMU)?

Accepted Answer

A unit of mass approximately equal to the mass of one proton or one neutron.

Question 16

Which of the following statements about electrons is correct?

Accepted Answer

Electrons are negatively charged and are found in orbitals around the nucleus.

Question 17

A patient is given a tracer containing a radioactive isotope of iodine. Which property of this isotope allows it to be used for imaging in the body?

Accepted Answer

It emits radiation that can be detected by medical equipment.

Question 18

Which of the following is true about compounds?

Accepted Answer

A compound consists of two or more different elements chemically bonded together.

Question 19

If an atom has 11 protons, 12 neutrons, and 11 electrons, what is its atomic mass in daltons?

Accepted Answer

$$11 + 12 = 23$$ daltons

Question 20

Which of the following best explains why isotopes of the same element have nearly identical chemical properties?

Accepted Answer

They have the same number of electrons and protons, which determine chemical behavior.

Atomic Structure and Elements in Biology: Study Guidance

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