Question 1

Which of the following statements best describes the difference between isotopes of the same element?

Accepted Answer

They have the same number of protons but different numbers of neutrons.

Question 2

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

Accepted Answer

$$16$$

Question 3

Which of the following is the correct electron configuration for magnesium ($$Z = 12$$)?

Accepted Answer

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

Question 4

Which group of the periodic table contains elements that are colorless, unreactive gases at room temperature?

Accepted Answer

Group 8A (Noble gases)

Question 5

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

Accepted Answer

$$69.7$$ amu

Question 6

Which of the following best explains why alkali metals are never found in nature in their pure state?

Accepted Answer

They are highly reactive and readily combine with other elements.

Question 7

What is the total number of electrons in a neutral atom of tin ($$Z = 50$$), and how many of these are valence electrons?

Accepted Answer

$$50$$ electrons, $$4$$ valence electrons

Question 8

Which of the following electron configurations represents a halogen in its ground state?

Accepted Answer

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

Question 9

Which of the following statements about the periodic table is correct?

Accepted Answer

Elements in the same group have similar chemical properties.

Question 10

A certain atom has 28 protons, 28 electrons, and 32 neutrons. What is the correct symbol for this isotope?

Accepted Answer

$$^{60}_{28}Ni$$

Question 11

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

Accepted Answer

Electrons occupy quantized energy levels and are described by wave functions.

Question 12

How many electrons are present in an atom that has its first and second shells filled and has four electrons in its third shell? What is the element?

Accepted Answer

$$14$$ electrons; silicon (Si)

Question 13

Which of the following is the general valence-shell electron configuration for elements in group 6A?

Accepted Answer

$$ns^2$$ $$np^4$$

Question 14

Which of the following elements is a metalloid?

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

The symbol with five dots, one on each side and one paired.

Question 16

Which of the following statements about subatomic particles is correct?

Accepted Answer

Protons and neutrons are found in the nucleus, while electrons are found outside the nucleus.

Question 17

Which of the following best explains why electrons in the same orbital must have opposite spins?

Accepted Answer

The Pauli exclusion principle states that no two electrons in the same atom can have the same set of quantum numbers.

Question 18

Which of the following is the correct order of filling for the first four subshells according to the Aufbau principle?

Accepted Answer

$$1s \rightarrow 2s \rightarrow 2p \rightarrow 3s$$

Question 19

Which of the following elements has the electron configuration $$[Ar] 4s^2$ 3d$$^{10}$$ 4p^2$?

Accepted Answer

Germanium (Ge)

Atoms and the Periodic Table: Fundamentals for GOB Chemistry

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