Q: What is the charge on an ion with 17 protons and 18 electrons?

$$\text{Ion charge} = 17 - 18 = -1$$

Q: A sample of chlorine contains 75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu). What is the atomic mass of chlorine? (Use the formula: $$\text{Atomic mass} = (\text{fraction}_1 \times \text{mass}_1) + (\text{fraction}_2 \times \text{mass}_2))$$

$$\text{Atomic mass} = (0.7577 \times 34.97) + (0.2423 \times 36.97) = 35.45$$ amu

Question 1

Which experiment provided the first evidence that atoms have a small, dense nucleus, and what was the key observation?

Accepted Answer

Rutherford's gold foil experiment; the observation that a small fraction of alpha particles were deflected at large angles.

Question 2

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 3

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

Accepted Answer

12 protons, 12 neutrons, 12 electrons

Question 4

Which property is NOT typical of metals?

Accepted Answer

Tends to gain electrons in chemical reactions

Question 5

What is the charge on an ion with 17 protons and 18 electrons?

Accepted Answer

$$	ext{Ion charge} = 17 - 18 = -1$$

Question 6

Which element is classified as a metalloid and is widely used in the manufacture of electronic devices due to its semiconducting properties?

Accepted Answer

Silicon

Question 7

A sample of chlorine contains 75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu). What is the atomic mass of chlorine? (Use the formula: $$	ext{Atomic mass} = (	ext{fraction}_1 	imes 	ext{mass}_1) + (	ext{fraction}_2 	imes 	ext{mass}_2))$$

Accepted Answer

$$	ext{Atomic mass} = (0.7577 	imes 34.97) + (0.2423 	imes 36.97) = 35.45$$ amu

Question 8

Which of the following best explains why the periodic law was considered a scientific law and not a theory?

Accepted Answer

It summarized many observations about recurring properties of elements but did not explain why those patterns occurred.

Question 9

Which element has the chemical symbol 'K' and what is the origin of this symbol?

Accepted Answer

Potassium; from the Latin 'kalium'

Question 10

A fluorine atom gains one electron during a chemical reaction. What ion is formed and what is its charge?

Accepted Answer

$$	ext{F}^-$$, charge = -1$

Question 11

Which group of elements is characterized by being inert and having very low chemical reactivity?

Accepted Answer

Noble gases

Question 12

Which of the following is a correct isotope symbol for an atom with 6 protons and 8 neutrons?

Accepted Answer

$$^{14}_{6}	ext{C}$$

Question 13

Which of the following best describes the distribution of mass and volume in an atom?

Accepted Answer

Most of the mass is in the nucleus, while most of the volume is occupied by electrons.

Question 14

Which of the following elements is a halogen?

Accepted Answer

Chlorine

Question 15

Which of the following is a real-world application of a radioactive isotope?

Accepted Answer

Technetium-99 is used in medical imaging to diagnose disease.

Question 16

Which of the following best describes the trend for main-group elements forming ions?

Accepted Answer

They tend to form ions with the same number of valence electrons as the nearest noble gas.

Question 17

Which of the following is the correct formula for calculating the number of neutrons in an isotope?

Accepted Answer

$$	ext{Number of neutrons} = 	ext{mass number} - 	ext{atomic number}$$

Question 18

Which of the following elements is most likely to lose one electron to form a cation in a chemical reaction?

Accepted Answer

Sodium

Question 19

Which scientist is credited with the first modern atomic theory that explained the law of conservation of mass and the law of definite proportions?

Accepted Answer

John Dalton

Question 20

Which of the following best explains why matter is usually electrically neutral?

Accepted Answer

Because the number of protons equals the number of electrons in an atom.

Atoms and Elements: Foundations of Matter and the Periodic Table

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