Q: A neutral atom of chlorine has an atomic number of 17 and a mass number of 37. How many neutrons does it contain?

$$\text{Number of neutrons} = 37 - 17 = 20$$

Question 1

Which of the following statements best explains why potassium (K) is classified as a metal?

Accepted Answer

Potassium is shiny, malleable, and a good conductor of heat and electricity.

Question 2

A neutral atom of chlorine has an atomic number of 17 and a mass number of 37. How many neutrons does it contain?

Accepted Answer

$$	ext{Number of neutrons} = 37 - 17 = 20$$

Question 3

Which element is a metalloid located in Period 3 of the periodic table?

Accepted Answer

Silicon (Si)

Question 4

Which of the following electron arrangements corresponds to the element sulfur (S)?

Accepted Answer

$$2,8,6$$

Question 5

A sample of magnesium contains three isotopes: Mg-24 (78.70%), Mg-25 (10.13%), and Mg-26 (11.17%). Which isotope is the most abundant, and how does this relate to the atomic mass of magnesium?

Accepted Answer

Mg-24 is the most abundant, and the atomic mass of magnesium ($$24.31\ 	ext{amu}) is $$closest to 24.

Question 6

Which of the following elements has the highest ionization energy?

Accepted Answer

Fluorine (F)

Question 7

A farmer applies potassium chloride (KCl) fertilizer to a field. Potassium is essential for plant growth. Which group and period does potassium belong to, and how many protons does a potassium atom have?

Accepted Answer

Group 1, Period 4; 19 protons

Question 8

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

Accepted Answer

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

Question 9

Which of the following is the correct Lewis symbol for an atom of phosphorus (P)?

Accepted Answer

Five dots around the symbol $$P$$

Question 10

A neutral atom of zinc has an atomic number of 30 and a mass number of 68. How many protons, neutrons, and electrons does it have?

Accepted Answer

30 protons, 38 neutrons, 30 electrons

Question 11

Which of the following elements is a halogen and a nonmetal found in Period 5?

Accepted Answer

Iodine (I)

Question 12

Which of the following best explains why the metallic character increases as you move down a group in the periodic table?

Accepted Answer

Valence electrons are farther from the nucleus and are more easily lost.

Question 13

Which of the following electron arrangements represents an atom with three energy levels and five electrons in its outermost level?

Accepted Answer

$$2,8,5$$

Question 14

Which of the following is a correct statement about isotopes?

Accepted Answer

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

Question 15

Which of the following elements has the greatest metallic character?

Accepted Answer

Sodium (Na)

Question 16

A magnesium atom forms a $$Mg^{2+}$$ ion by losing electrons. From which energy level are these electrons lost?

Accepted Answer

$$n=3$$ energy level

Question 17

Which of the following best describes the trend in ionization energy as you move down a group in the periodic table?

Accepted Answer

Ionization energy decreases because valence electrons are farther from the nucleus.

Question 18

Which of the following is the correct atomic symbol for a tin isotope with 50 protons and 76 neutrons?

Accepted Answer

$$^{126}_{50}Sn$$

Question 19

Which of the following elements is a noble gas in Period 4?

Accepted Answer

Krypton (Kr)

Question 20

Which of the following electron arrangements corresponds to an atom of potassium (K)?

Accepted Answer

$$2,8,8,1$$

Atoms and the Periodic Table: Structure, Properties, and Trends

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