Q: Which of the following is the correct electron-dot (Lewis) symbol for an element in group 5A?

$$\text{X} \cdot \cdot \cdot \cdot \cdot$$

Question 1

Which statement best summarizes John Dalton's atomic theory as it relates to chemical reactions?

Accepted Answer

Chemical reactions change only the way atoms are combined in compounds.

Question 2

A neutral atom of phosphorus has an atomic number of 15 and a mass number of 31. How many protons, neutrons, and electrons does it contain?

Accepted Answer

15 protons, 16 neutrons, 15 electrons

Question 3

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

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 mass of gallium? (Round to two decimal places)

Accepted Answer

$$69.72 \, 	ext{amu}$$

Question 5

Which property is NOT characteristic of metals?

Accepted Answer

Brittle

Question 6

Which group of the periodic table contains elements that are colorless, odorless, and chemically unreactive under normal conditions?

Accepted Answer

Group 8A (Noble gases)

Question 7

Which of the following electron configurations represents a nitrogen atom?

Accepted Answer

$$1s^2$$\,$$2s^2$$\,$$2p^3$$

Question 8

Which principle states that electrons fill the lowest energy orbitals first?

Accepted Answer

Aufbau Principle

Question 9

A tin atom has 50 electrons. How many electrons are in its valence shell, and what is the valence-shell configuration?

Accepted Answer

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

Question 10

Which of the following best explains why elements in the same group of the periodic table have similar chemical properties?

Accepted Answer

They have similar electron configurations in their valence shells.

Question 11

Which element is a metalloid and would be expected to have properties intermediate between metals and nonmetals?

Accepted Answer

Silicon (Si)

Question 12

Which of the following is the correct nuclear symbol for an isotope of iron with 26 protons and 30 neutrons?

Accepted Answer

$$^{56}_{26}	ext{Fe}$$

Question 13

Which of the following statements about electron shells and subshells is correct?

Accepted Answer

Shells are divided into subshells, which are divided into orbitals.

Question 14

A neutral atom has its first and second shells filled and four electrons in its third shell. What is the element?

Accepted Answer

Silicon (Si)

Question 15

Which of the following is the correct electron-dot (Lewis) symbol for an element in group 5A?

Accepted Answer

$$	ext{X} \cdot \cdot \cdot \cdot \cdot$$

Question 16

Which of the following best describes the quantum mechanical model of the atom?

Accepted Answer

Electrons are restricted to certain energy values and occupy regions of high probability called orbitals.

Question 17

Which rule states that each orbital in a subshell is singly occupied before any orbital is doubly occupied?

Accepted Answer

Hund's Rule

Question 18

Which of the following elements is most likely to be found as a diatomic molecule in nature and is highly reactive?

Accepted Answer

Chlorine (Cl)

Question 19

Which of the following best explains why the nucleus of an atom stays together despite the repulsion between protons?

Accepted Answer

The strong nuclear force holds the protons and neutrons together.

Question 20

Which of the following is the correct shorthand electron configuration for chlorine (Cl)?

Accepted Answer

$$[Ne] 3s^2$ 3p^5$

Atoms and the Periodic Table: Foundations of GOB Chemistry

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