Question 1

Which statement best describes Dalton’s contribution to atomic theory?

Accepted Answer

He transformed the philosophical idea of atoms into a scientific theory based on experimental evidence.

Question 2

Which experiment led to the discovery of the electron?

Accepted Answer

Cathode ray tube experiment

Question 3

An atom of phosphorus has an atomic number $$Z = 15$$ and a mass number $$A = 31. $$How many neutrons does it contain?

Accepted Answer

$$16$$

Question 4

Calculate the average atomic mass of an element with two isotopes: $$^{10}X ($$abundance $$75	ext{%}$$, mass $$10.012 u) $$and $$^{11}X ($$abundance $$25	ext{%}$$, mass $$11.009 u).$$

Accepted Answer

$$10.257 u$$

Question 5

Which of the following best explains why the mass of an atom is concentrated in its nucleus?

Accepted Answer

The nucleus contains protons and neutrons, which are much heavier than electrons.

Question 6

What is the molar mass of glucose ($$C_6H_{12}O_6$)? (Atomic masses: C = 12.01$ u, H = 1.01$ u, O = 16.00$ u)

Accepted Answer

$$180.16 g/$$mol

Question 7

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Angular momentum quantum number ($$l)$$

Question 8

According to the Bohr model, how many electrons can occupy the M shell ($$n=3$$)?

Accepted Answer

$$18$$

Question 9

Which principle states that no two electrons in an atom can have the same set of four quantum numbers?

Accepted Answer

Pauli exclusion principle

Question 10

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of CO_2$. How many moles of CO_2$ are present?

Accepted Answer

$$0.50$$ mol

Question 11

Which of the following is a consequence of the Heisenberg Uncertainty Principle?

Accepted Answer

It is impossible to know both the exact position and momentum of an electron simultaneously.

Question 12

What is the energy released (in J) when the mass defect $$\Delta m = 0.439 	imes 10$$^{-27}$$ kg? (c = 3.0$$ 	imes $$10^8 m/s)$$

Accepted Answer

$$3.95 	imes 10$$^{-11}$$ J

Question 13

Which electron configuration represents a neutral atom of chlorine ($$Z=17$$)?

Accepted Answer

$$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^5$$

Question 14

Which of the following best describes the difference between atomic mass and molar mass?

Accepted Answer

Atomic mass is the mass of one atom in atomic mass units (u), while molar mass is the mass of one mole of atoms in grams.

Question 15

Which quantum number describes the orientation of an orbital in space?

Accepted Answer

Magnetic quantum number ($$m_l)$$

Question 16

A sodium chloride crystal is best described by which term?

Accepted Answer

Formula mass

Question 17

Which rule explains why electrons fill degenerate orbitals singly before pairing up?

Accepted Answer

Hund’s rule

Question 18

How many orbitals are present in the $$n=2$$ energy level?

Accepted Answer

$$4$$

Question 19

Which of the following is the correct order of filling for the first four electron subshells according to the Aufbau principle?

Accepted Answer

$$1s, 2s, 2p, 3s$$

Atomic Structure and Quantum Theory: Mini-Textbook Study Notes

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