Question 1

Which statement best describes the difference between isotopes of the same element?

Accepted Answer

Isotopes have identical atomic numbers but different mass numbers due to varying numbers of neutrons.

Question 2

A neutral atom of phosphorus has a mass number of 31. How many neutrons does it contain?

Accepted Answer

16 neutrons

Question 3

Which of the following is NOT an assumption of atomic theory as described in the study materials?

Accepted Answer

Atoms can be divided into smaller particles during chemical reactions.

Question 4

Gallium has two naturally occurring isotopes: 60.4% Ga-69 (mass = 68.9257 amu) and 39.6% Ga-71 (mass = 70.9248 amu). What is the atomic weight of gallium? Use the formula $	ext{Atomic weight} = \sum[(	ext{isotopic abundance}) 	imes (	ext{isotopic mass})]$.

Accepted Answer

$69.7$ amu

Question 5

Which element is identified by the atomic number $Z = 28$ and contains 32 neutrons?

Accepted Answer

Nickel (Ni)

Question 6

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

Accepted Answer

Group 1A (Alkali metals)

Question 7

What is the electron configuration for magnesium ($Z = 12$)?

Accepted Answer

$1s^2 2s^2 2p^6 3s^2$

Question 8

Which of the following elements is a metalloid?

Accepted Answer

Silicon (Si)

Question 9

How many valence electrons does a tin (Sn) atom have, and what is its valence-shell configuration?

Accepted Answer

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

Question 10

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

Accepted Answer

They have completely filled valence shells.

Question 11

What is the general valence-shell electron configuration for elements in group 6A?

Accepted Answer

$ns^2 np^4$

Question 12

Which of the following statements about subatomic particles is correct?

Accepted Answer

Protons and neutrons have nearly the same mass, but electrons are much lighter.

Question 13

An atom has its first and second shells filled and has four electrons in its third shell. What is the atomic number and identity of this element?

Accepted Answer

Atomic number 14; Silicon (Si)

Question 14

Which of the following electron configurations represents chlorine ($Z = 17$)?

Accepted Answer

$1s^2 2s^2 2p^6 3s^2 3p^5$

Question 15

Which of the following best describes the arrangement of electrons in an atom according to the quantum mechanical model?

Accepted Answer

Electrons are restricted to certain energy values and are grouped into shells, subshells, and orbitals.

Question 16

Which element would have the following electron-dot (Lewis) symbol: a symbol with five dots arranged around it?

Accepted Answer

Nitrogen (N)

Question 17

Which of the following elements is most likely to be found as a colorful and corrosive nonmetal in nature only in combination with other elements?

Accepted Answer

Bromine (Br)

Question 18

Which of the following best describes the relationship between atomic number and the number of electrons in a neutral atom?

Accepted Answer

The atomic number equals the number of electrons in a neutral atom.

Question 19

Which of the following is the correct electron configuration for sodium ($Z = 11$) using noble gas shorthand notation?

Accepted Answer

$[Ne] 3s^1$

Atoms and the Periodic Table: Fundamentals for GOB Chemistry

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