Q: Which equation correctly calculates the average atomic weight of an element given its isotopic abundances and masses?

$$\sum [(\text{isotopic abundance}) \times (\text{isotopic mass})]$$

Question 1

Which of the following statements best describes the major assumptions of atomic theory as presented in the study materials?

Accepted Answer

Chemical compounds consist of atoms combined in specific ratios, and chemical reactions only change the way atoms are combined.

Question 2

A neutral atom of phosphorus has an atomic number $$Z = 15$$ and a mass number $$A = 31. $$How many neutrons does it contain?

Accepted Answer

16 neutrons

Question 3

Which subatomic particle has a mass approximately $$1/1836$$ that of a proton and carries a negative charge?

Accepted Answer

Electron

Question 4

Nickel has atomic number $$Z = 28$$ and mass number $$A = 60. $$How many electrons and neutrons are present in a neutral atom of nickel?

Accepted Answer

28 electrons, 32 neutrons

Question 5

Which equation correctly calculates the average atomic weight of an element given its isotopic abundances and masses?

Accepted Answer

$$\sum [(	ext{isotopic abundance}) 	imes (	ext{isotopic mass})]$$

Question 6

Gallium has two naturally occurring isotopes: $$^{69}	ext{Ga} ($$mass $$= 68.9257$$ amu, abundance $$= 60.4\%) $$and $$^{71}	ext{Ga} ($$mass $$= 70.9248$$ amu, abundance $$= 39.6\%). $$What is the atomic weight of gallium? (Round to one decimal place)

Accepted Answer

$$69.7$$ amu

Question 7

Which group of the periodic table contains elements that are soft, highly reactive metals and are never found in nature in a pure state?

Accepted Answer

Group 1A (Alkali metals)

Question 8

Which of the following elements is classified as a metalloid based on its position in the periodic table?

Accepted Answer

Silicon (Si)

Question 9

Which property is shared by all elements in the same vertical column (group) of the periodic table?

Accepted Answer

They have similar chemical properties due to similar valence electron configurations.

Question 10

Which of the following best explains why noble gases are labeled 'noble'?

Accepted Answer

They have a lack of chemical reactivity and do not readily combine with other elements.

Question 11

According to the quantum mechanical model, which statement about electron energy levels is correct?

Accepted Answer

Electrons are restricted to certain quantized energy values.

Question 12

How many electrons can the third shell of an atom hold?

Accepted Answer

18 electrons

Question 13

Which subshell contains three orbitals and can hold a maximum of six electrons?

Accepted Answer

p subshell

Question 14

What is the electron configuration for sodium ($$Z = 11) in $$both complete and shorthand notation?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^1 or$$ $$[Ne] 3s^1$

Question 15

Which rule states that two or more orbitals with the same energy are each half-filled by one electron before any one orbital is completely filled by the addition of the second electron?

Accepted Answer

Hund's rule

Question 16

A tin atom ($$Z = 50) $$has electrons distributed in shells as follows: $$2, 8, 18, 18, 4. $$How many valence electrons does tin have, and what is its valence-shell configuration?

Accepted Answer

4 valence electrons; $$5s^2$$ $$5p^2$$

Question 17

Which electron-dot (Lewis) symbol correctly represents an element in group 5A?

Accepted Answer

The symbol with five dots, four distributed singly and one paired.

Question 18

Which element has the electron configuration $$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^2$$?

Accepted Answer

Silicon (Si)

Question 19

If an atom has its first and second shells filled and four electrons in its third shell, what is its atomic number and which element is it?

Accepted Answer

$$Z = 14$$, Silicon (Si)

Question 20

Which of the following best describes the relationship between electron configuration and the periodic table?

Accepted Answer

Elements in the same group have similar valence shell electron configurations.

Atoms and the Periodic Table: Foundations for Anatomy & Physiology

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