$$2n^2 = 2$$ \times $$3^2 = 18$ electrons

$$0.7577 \times 35.0 + 0.2423 \times 37.0 = 35.5$$ amu

Question 1

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 2

A neutral atom of sodium (Na) has an atomic number of 11 and a mass number of 23. How many protons, neutrons, and electrons does it contain?

Accepted Answer

11 protons, 12 neutrons, 11 electrons

Question 3

Which experiment led to the discovery that the atom is mostly empty space with a small, dense, positively charged nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 4

Which of the following electron configurations represents a chlorine atom (atomic number 17)?

Accepted Answer

$$1s^22s^22$p^63s^23$p^5$$

Question 5

Which of the following best explains why the atomic mass of chlorine is not a whole number?

Accepted Answer

It is the weighted average of the masses of all naturally occurring isotopes of chlorine.

Question 6

Which of the following elements is most likely to form a cation by losing two electrons to achieve a noble gas configuration?

Accepted Answer

Calcium (Ca)

Question 7

What is the maximum number of electrons that can be held in the $$n = 3$$ principal energy level?

Accepted Answer

$$2n^2 = 2$$ 	imes $$3^2 = 18$ electrons

Question 8

Which of the following statements about the periodic table is correct?

Accepted Answer

Elements in the same group have similar chemical properties.

Question 9

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

Accepted Answer

Atomic size increases due to higher principal energy levels.

Question 10

Which of the following ions is isoelectronic with neon ($$Ne$$)?

Accepted Answer

$$N^{3-}$$

Question 11

Which of the following is a correct statement about the Bohr model of the atom?

Accepted Answer

Electrons exist in fixed energy levels and can move between them by absorbing or emitting energy.

Question 12

Which principle states that each orbital can hold a maximum of two electrons with opposite spins?

Accepted Answer

Pauli Exclusion Principle

Question 13

A sample of chlorine contains 75.77% $$^{35}Cl ($$mass = 35.0 amu) and 24.23% $$^{37}Cl ($$mass = 37.0 amu). What is the atomic mass of chlorine?

Accepted Answer

$$0.7577 	imes 35.0 + 0.2423 	imes 37.0 = 35.5$$ amu

Question 14

Which of the following best describes the trend in ionization energy across a period from left to right?

Accepted Answer

Ionization energy increases due to increasing nuclear charge and decreasing atomic size.

Question 15

Which scientist's model first proposed that electrons move in quantized orbits around the nucleus?

Accepted Answer

Niels Bohr

Question 16

Which of the following is a property of metals?

Accepted Answer

High thermal and electrical conductivity

Question 17

Which of the following statements about electron affinity is correct?

Accepted Answer

Electron affinity generally increases across a period from left to right.

Question 18

Which of the following best describes the difference between the Bohr model and the quantum mechanical model of the atom?

Accepted Answer

The quantum mechanical model describes electrons as existing in orbitals with a probability distribution, not fixed orbits.

Question 19

Which of the following ions is smaller than its parent atom?

Accepted Answer

$$Fe^{3+}$$

Chapter 2: The Periodic Table – Structure, Atomic Theory, and Electron Arrangement

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