Q: Given the following isotopes of chlorine: $$^{35}\mathrm{Cl} (75.8$$% abundance, mass = 34.97 u) and $$^{37}\mathrm{Cl} (24.2$$% abundance, mass = 36.97 u), what is the atomic mass of chlorine?

$$(0.758 \times 34.97) + (0.242 \times 36.97) = 35.45 u$$

Q: A sample of boron contains 20% $$^{10}\mathrm{B} ($$mass = 10.01 u) and 80% $$^{11}\mathrm{B} ($$mass = 11.01 u). What is the atomic mass of boron?

$$(0.20 \times 10.01) + (0.80 \times 11.01) = 10.81 u$$

Q: A sample of magnesium contains three isotopes: $$^{24}\mathrm{Mg} (79$$% abundance, mass = 23.99 u), $$^{25}\mathrm{Mg} (10$$% abundance, mass = 24.99 u), and $$^{26}\mathrm{Mg} (11$$% abundance, mass = 25.98 u). What is the atomic mass of magnesium?

$$(0.79 \times 23.99) + (0.10 \times 24.99) + (0.11 \times 25.98) = 24.31 u$$

Question 1

Which of the following correctly matches the element name with its symbol?

Accepted Answer

Iron: Fe

Question 2

An atom has an atomic number of 17 and a mass number of 35. How many neutrons does it have?

Accepted Answer

$$35 - 17 = 18$$ neutrons

Question 3

Which of the following statements about subatomic particles is correct?

Accepted Answer

Electrons are negatively charged and found outside the nucleus.

Question 4

Which element is located in Group 2, Period 3 of the periodic table?

Accepted Answer

Magnesium (Mg)

Question 5

Given the following isotopes of chlorine: $$^{35}\mathrm{Cl} (75.8$$% abundance, mass = 34.97 u) and $$^{37}\mathrm{Cl} (24.2$$% abundance, mass = 36.97 u), what is the atomic mass of chlorine?

Accepted Answer

$$(0.758 	imes 34.97) + (0.242 	imes 36.97) = 35.45 u$$

Question 6

Which of the following elements is a metalloid?

Accepted Answer

Silicon (Si)

Question 7

A neutral atom of sulfur has an atomic number of 16. How many electrons does it have?

Accepted Answer

16 electrons

Question 8

Which of the following best describes the location and charge of a neutron?

Accepted Answer

Located in the nucleus, no charge

Question 9

Which element is a nonmetal and is found in Group 17 of the periodic table?

Accepted Answer

Chlorine (Cl)

Question 10

A sample of boron contains 20% $$^{10}\mathrm{B} ($$mass = 10.01 u) and 80% $$^{11}\mathrm{B} ($$mass = 11.01 u). What is the atomic mass of boron?

Accepted Answer

$$(0.20 	imes 10.01) + (0.80 	imes 11.01) = 10.81 u$$

Question 11

Which of the following elements is most likely to be a good conductor of electricity?

Accepted Answer

Copper (Cu)

Question 12

If an atom has 12 protons, 12 neutrons, and 12 electrons, what is its atomic number and mass number?

Accepted Answer

Atomic number: 12, Mass number: 24

Question 13

Which of the following is the correct symbol for the element phosphorus?

Accepted Answer

P

Question 14

A hospital uses a radioactive isotope of iodine, $$^{131}\mathrm{I}$$, for thyroid imaging. If $$^{131}\mathrm{I}$$ has 53 protons, how many neutrons does it have?

Accepted Answer

$$131 - 53 = 78$$ neutrons

Question 15

Which of the following elements is in Period 2 and is a nonmetal?

Accepted Answer

Oxygen (O)

Question 16

A certain isotope of carbon has 6 protons and 8 neutrons. What is its symbol?

Accepted Answer

$$^{14}\mathrm{C}$$

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

A student is given an unknown element. It is shiny, malleable, and conducts electricity. Based on these properties, to which category does this element most likely belong?

Accepted Answer

Metal

Question 19

Which of the following elements is in the same group as sodium (Na)?

Accepted Answer

Potassium (K)

Question 20

A sample of magnesium contains three isotopes: $$^{24}\mathrm{Mg} (79$$% abundance, mass = 23.99 u), $$^{25}\mathrm{Mg} (10$$% abundance, mass = 24.99 u), and $$^{26}\mathrm{Mg} (11$$% abundance, mass = 25.98 u). What is the atomic mass of magnesium?

Accepted Answer

$$(0.79 	imes 23.99) + (0.10 	imes 24.99) + (0.11 	imes 25.98) = 24.31 u$$

Atoms and Elements: Structure, Symbols, and Isotopes

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