Q: Which formula correctly calculates the atomic mass of an atom?

$$\text{Atomic mass} = \text{Number of protons} + \text{Number of neutrons}$$

Question 1

Which of the following statements best explains why oxygen, carbon, hydrogen, and nitrogen make up about 96% of living matter?

Accepted Answer

They have unique chemical properties that allow them to form a wide variety of complex molecules essential for life.

Question 2

A patient is diagnosed with hypothyroidism due to a deficiency of a trace element. Which element is most likely deficient, and what is its biological role?

Accepted Answer

Iodine (I); required for thyroid hormone production

Question 3

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 4

A radioactive isotope of carbon, $$^{14}C$$, is used in medical research. What makes $$^{14}C$$ radioactive?

Accepted Answer

It has an unstable nucleus that spontaneously emits particles and energy.

Question 5

Which formula correctly calculates the atomic mass of an atom?

Accepted Answer

$$	ext{Atomic mass} = 	ext{Number of protons} + 	ext{Number of neutrons}$$

Question 6

Which statement about electron shells is correct?

Accepted Answer

Electrons in the outermost shell have the highest potential energy.

Question 7

A sodium atom ($$Na) $$has 11 electrons. After losing one electron to form $$Na^+$$, what is the charge and electron configuration of the ion?

Accepted Answer

Charge: $$+1$$; 10 electrons

Question 8

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of valence electrons between atoms

Question 9

Water ($$H_2O) is a $$compound. Which statement best explains why?

Accepted Answer

It consists of two different elements chemically combined in a fixed ratio.

Question 10

Which of the following elements is a trace element required by vertebrates but not by all organisms?

Accepted Answer

Iodine (I)

Question 11

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

Accepted Answer

Atomic number: 6; Mass number: 14

Question 12

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

Accepted Answer

A molecule consists of two or more atoms bonded together, while a compound consists of two or more different elements bonded together.

Question 13

Which of the following is true about valence electrons?

Accepted Answer

They determine the chemical behavior of an atom.

Question 14

A magnesium atom ($$Mg) $$has 12 electrons. When it forms a $$Mg^{2+}$$ ion, how many electrons does it have?

Accepted Answer

10

Question 15

Which of the following best explains why noble gases are chemically inert?

Accepted Answer

They have full valence electron shells.

Question 16

Which of the following equations correctly represents the formation of sodium chloride ($$NaCl) $$from its elements?

Accepted Answer

$$Na + Cl \rightarrow NaCl$$

Question 17

Which statement best describes the role of radioactive isotopes in biological research?

Accepted Answer

They are used as tracers to follow the fate of atoms in metabolic processes.

Question 18

Which of the following best describes an ionic bond?

Accepted Answer

A bond formed by the attraction between oppositely charged ions

Question 19

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

Accepted Answer

They are used to diagnose and treat thyroid disorders.

Chap2 biology

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