Q: A certain isotope of gallium has an atomic mass of $$69$$ and a percent abundance of $$60.10\%. $$Another isotope has an atomic mass of $$71$$ and a percent abundance of $$39.90\%. $$What is the atomic mass of gallium?

$$(0.6010 \times 69) + (0.3990 \times 71) = 69.80$$

Question 1

Which of the following statements best describes an element?

Accepted Answer

An element is a pure substance that cannot be broken down into simpler substances by chemical means.

Question 2

Which of the following elements is a metalloid?

Accepted Answer

Silicon (Si)

Question 3

What is the correct chemical symbol for the element with the Latin name 'aurum'?

Accepted Answer

Au

Question 4

Which group on the periodic table contains the noble gases?

Accepted Answer

Group 8A (18)

Question 5

A neutral atom of magnesium has an atomic number of 12 and a mass number of 24. How many neutrons does it have?

Accepted Answer

$$24 - 12 = 12$$ neutrons

Question 6

Which of the following best describes the trend in atomic size across a period from left to right?

Accepted Answer

Atomic size decreases due to increased nuclear charge.

Question 7

Which element is most likely to form a cation by losing one electron?

Accepted Answer

Sodium (Na)

Question 8

A certain isotope of gallium has an atomic mass of $$69$$ and a percent abundance of $$60.10\%. $$Another isotope has an atomic mass of $$71$$ and a percent abundance of $$39.90\%. $$What is the atomic mass of gallium?

Accepted Answer

$$(0.6010 	imes 69) + (0.3990 	imes 71) = 69.80$$

Question 9

Which of the following electron configurations represents a noble gas?

Accepted Answer

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

Question 10

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 11

Which element has the highest ionization energy among the following?

Accepted Answer

Fluorine (F)

Question 12

What is the maximum number of electrons that can occupy the 3p sublevel?

Accepted Answer

$$6$$

Question 13

Which of the following best describes the Pauli exclusion principle?

Accepted Answer

Each orbital can hold a maximum of two electrons with opposite spins.

Question 14

Which of the following elements is a halogen?

Accepted Answer

Chlorine (Cl)

Question 15

Which of the following statements about metals is true?

Accepted Answer

Metals are good conductors of heat and electricity.

Question 16

How many valence electrons does a neutral atom of phosphorus (P) have?

Accepted Answer

$$5$$

Question 17

Which of the following best describes the trend in metallic character across a period from left to right?

Accepted Answer

Metallic character decreases.

Question 18

Which of the following is the correct electron configuration for potassium (K)?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^6$$ $$4s^1$$

Question 19

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

Accepted Answer

Groups are vertical columns and periods are horizontal rows.

Question 20

A farmer applies a fertilizer containing potassium (K) and magnesium (Mg) to crops. Which group do these elements belong to?

Accepted Answer

Alkali metals and alkaline earth metals

Atoms and Elements: Structure, Properties, and Periodic Trends

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