Q: A sample of gallium contains 60.4% $$^{69}\mathrm{Ga} ($$mass = 68.9257 amu) and 39.6% $$^{71}\mathrm{Ga} ($$mass = 70.9248 amu). What is the atomic weight of gallium? (Round to one decimal place.)

$$0.604 \times 68.9257 + 0.396 \times 70.9248 = 69.7$$ amu

Question 1

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

Accepted Answer

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

Question 2

A neutral atom of sulfur has an atomic number of 16 and a mass number of 32. How many neutrons does it contain?

Accepted Answer

$$32 - 16 = 16$$ neutrons

Question 3

Which of the following elements is classified as a metalloid and is commonly used in computer chips due to its semiconducting properties?

Accepted Answer

Silicon (Si)

Question 4

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

Accepted Answer

Group 8A (Noble gases)

Question 5

A sample of gallium contains 60.4% $$^{69}\mathrm{Ga} ($$mass = 68.9257 amu) and 39.6% $$^{71}\mathrm{Ga} ($$mass = 70.9248 amu). What is the atomic weight of gallium? (Round to one decimal place.)

Accepted Answer

$$0.604 	imes 68.9257 + 0.396 	imes 70.9248 = 69.7$$ amu

Question 6

Which of the following electron configurations represents a neutral atom of magnesium ($$Z = 12$$)?

Accepted Answer

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

Question 7

Which of the following best explains why alkali metals (Group 1A) are never found in nature in their pure elemental form?

Accepted Answer

They are highly reactive and readily combine with other elements, especially with water and oxygen.

Question 8

Which of the following statements about the arrangement of electrons in atoms is correct?

Accepted Answer

Electrons fill the lowest energy orbitals first, and each orbital can hold a maximum of two electrons with opposite spins.

Question 9

A neutral atom has 28 protons and a mass number of 60. What is the identity of the element and how many neutrons does it have?

Accepted Answer

Nickel (Ni), $$60 - 28 = 32$$ neutrons

Question 10

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

Accepted Answer

The symbol N with five dots: one on each side and one paired (e.g., one pair and three singles)

Question 11

Which of the following elements is a transition metal?

Accepted Answer

Iron (Fe)

Question 12

Which of the following best describes the periodic trend in atomic radius as you move from left to right across a period in the periodic table?

Accepted Answer

Atomic radius decreases due to increasing nuclear charge pulling electrons closer.

Question 13

Which of the following is the correct shorthand electron configuration for chlorine ($$Z = 17$$)?

Accepted Answer

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

Question 14

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 in which subshells are they found?

Accepted Answer

4 valence electrons in the 5s and 5p subshells

Question 15

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 that give the probability of finding an electron in a particular region.

Question 16

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

Accepted Answer

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

Question 17

A patient is exposed to a radioactive isotope of iodine, $$^{131}\mathrm{I}$$, for thyroid imaging. How many protons, neutrons, and electrons are present in a neutral atom of $$^{131}\mathrm{I}$$?

Accepted Answer

53 protons, $$131 - 53 = 78$$ neutrons, 53 electrons

Question 18

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

Accepted Answer

Elements in the same group have similar chemical properties because they have the same number of valence electrons.

Question 19

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

Accepted Answer

They have completely filled valence shells, making them stable and unlikely to gain or lose electrons.

Atoms and the Periodic Table: Structured Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard