$$(0.6011 \times 68.9256) + (0.3989 \times 70.9247) = 69.72$$ amu

$$\text{ion charge} = \text{number of protons} - \text{number of electrons}$$

Question 1

Which statement best describes the contribution of Democritus and Leucippus to atomic theory?

Accepted Answer

They proposed that matter is made of tiny, indestructible particles called atoms.

Question 2

According to Dalton's atomic theory, which of the following is NOT true?

Accepted Answer

Atoms of different elements can have the same mass.

Question 3

Which experiment led to the conclusion that atoms have a small, dense nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 4

What is the charge and relative mass of an electron compared to a proton?

Accepted Answer

Charge: $$1-$$, Mass: nearly 2000 times less than a proton

Question 5

Which of the following best explains why most alpha particles passed through the gold foil in Rutherford’s experiment?

Accepted Answer

Atoms are mostly empty space.

Question 6

If an atom has 11 protons, 12 neutrons, and 10 electrons, what is its ion charge?

Accepted Answer

$$11 - 10 = 1+$$

Question 7

Which element is defined by having 6 protons in its nucleus?

Accepted Answer

Carbon

Question 8

What is the atomic number ($$Z) of an $$element with the symbol Na?

Accepted Answer

$$Z = 11$$

Question 9

Which property is NOT characteristic of metals?

Accepted Answer

They tend to gain electrons in chemical reactions.

Question 10

A sample of gallium contains 60.11% Ga-69 (mass 68.9256 amu) and 39.89% Ga-71 (mass 70.9247 amu). What is the atomic mass of gallium?

Accepted Answer

$$(0.6011 	imes 68.9256) + (0.3989 	imes 70.9247) = 69.72$$ amu

Question 11

Which group in the periodic table contains elements that are chemically inert?

Accepted Answer

Noble gases

Question 12

What is the mass number ($$A) of an $$isotope with 17 protons and 20 neutrons?

Accepted Answer

$$A = 37$$

Question 13

Which of the following elements is a metalloid and widely used in electronics?

Accepted Answer

Silicon

Question 14

Which of the following ions is an anion?

Accepted Answer

F$$^-$$

Question 15

If a neutral atom of chlorine has 17 protons and 18 neutrons, what is its isotope symbol?

Accepted Answer

$$\mathrm{^{35}_{17}Cl}$$

Question 16

Which statement about isotopes is correct?

Accepted Answer

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

Question 17

Which element is named after a scientist who helped discover radioactivity?

Accepted Answer

Curium

Question 18

What is the formula to calculate the charge of an ion?

Accepted Answer

$$	ext{ion charge} = 	ext{number of protons} - 	ext{number of electrons}$$

Question 19

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

Accepted Answer

Diagnosing diseases using technetium-99 in medical imaging

Atoms and Elements: Foundations of Matter and the Periodic Table

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