Q: Calculate the average atomic mass of an element with two isotopes: 60% abundance of isotope A (mass = 10 amu) and 40% abundance of isotope B (mass = 12 amu).

$$0.60 \times 10 + 0.40 \times 12 = 10.8$$ amu

Question 1

Which of the following statements best describes the difference between the modern periodic table and Mendeleev's original periodic table?

Accepted Answer

The modern periodic table arranges elements by increasing atomic number, while Mendeleev's table arranged them by increasing atomic mass.

Question 2

Which element is located in Period 3, Group 8A of the periodic table?

Accepted Answer

Argon (Ar)

Question 3

A neutral atom of calcium (Ca) has an atomic number of 20. How many protons and electrons does it have?

Accepted Answer

20 protons and 20 electrons

Question 4

Which of the following elements is a metalloid?

Accepted Answer

Silicon (Si)

Question 5

Which element has the highest ionization energy among the following?

Accepted Answer

Fluorine (F)

Question 6

What is the electron arrangement for magnesium (Mg)?

Accepted Answer

$$2, 8, 2$$

Question 7

Which of the following best describes a property of metals?

Accepted Answer

They are good conductors of electricity.

Question 8

An atom has 14 protons and 20 neutrons. What is its mass number and which element is it?

Accepted Answer

Mass number = $$34$$, Element = Silicon (Si)

Question 9

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 10

Calculate the average atomic mass of an element with two isotopes: 60% abundance of isotope A (mass = 10 amu) and 40% abundance of isotope B (mass = 12 amu).

Accepted Answer

$$0.60 	imes 10 + 0.40 	imes 12 = 10.8$$ amu

Question 11

Which element is most likely to be found as a shiny, malleable solid at room temperature?

Accepted Answer

Copper (Cu)

Question 12

Which group on the periodic table contains the noble gases?

Accepted Answer

Group 8A (18)

Question 13

What is the number of valence electrons in an atom of phosphorus (P)?

Accepted Answer

$$5$$

Question 14

Which of the following elements has the largest atomic size?

Accepted Answer

Potassium (K)

Question 15

A cation is formed when an atom:

Accepted Answer

Loses one or more electrons.

Question 16

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

Accepted Answer

Metallic character decreases.

Question 17

Which element is a nonmetal and is essential for respiration in humans?

Accepted Answer

Oxygen (O)

Question 18

If an atom has 17 protons, 20 neutrons, and 17 electrons, what is its atomic symbol?

Accepted Answer

$$^{37}_{17}\mathrm{Cl}$$

Question 19

Which of the following best explains why atomic size increases down a group?

Accepted Answer

Additional energy levels are added, increasing the distance between the nucleus and valence electrons.

Question 20

Which of the following is the correct Lewis symbol for aluminum (Al)?

Accepted Answer

Al with three dots around it

Atoms and Elements: Structure, Periodic Table, and Periodic Trends

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