Question 1

Which of the following best describes a scientific law?

Accepted Answer

A statement that summarizes a pattern found in nature, often expressed mathematically, and is supported by repeated experiments.

Question 2

Which of the following is the correct electron configuration for a neutral atom of magnesium ($$Z = 12$$)?

Accepted Answer

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

Question 3

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 4

Which element is a halogen?

Accepted Answer

Chlorine

Question 5

According to Dalton’s atomic theory, which statement is FALSE?

Accepted Answer

Atoms of the same element can have different masses.

Question 6

A neutral atom of phosphorus has an atomic number of 15 and a mass number of 31. How many neutrons does it have?

Accepted Answer

$$16$$

Question 7

Which of the following best describes a cation?

Accepted Answer

An ion with a positive charge formed by the loss of one or more electrons.

Question 8

Which of the following elements is a transition metal?

Accepted Answer

Iron

Question 9

How many electrons are present in a $$3p$$ subshell?

Accepted Answer

$$6$$

Question 10

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have completely filled valence electron shells.

Question 11

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

Accepted Answer

$$1s \rightarrow 2s \rightarrow 2p \rightarrow 3s \rightarrow 3p \rightarrow 4s \rightarrow 3d$$

Question 12

A student observes a chemical reaction and forms a hypothesis. What is the next step in the scientific method?

Accepted Answer

Design and perform experiments to test the hypothesis.

Question 13

Which of the following statements about the Bohr model and the quantum mechanical model of the atom is correct?

Accepted Answer

The Bohr model describes electrons in fixed orbits, while the quantum mechanical model describes electrons in probabilistic orbitals.

Question 14

How many valence electrons does a neutral atom of sulfur ($$Z = 16) $$have?

Accepted Answer

$$6$$

Question 15

Which of the following best describes a period on the periodic table?

Accepted Answer

A horizontal row of elements with the same number of electron shells.

Question 16

Which of the following ions has the same electron configuration as neon ($$Z = 10$$)?

Accepted Answer

$$\mathrm{Na}^+$$

Question 17

A sample contains $$3.0 	imes 10$$^{23}$$ atoms of carbon. How many moles of carbon are present? (N_A = 6.022$$ 	imes $$10^{23}$$\ \mathrm{mol}^{-1}$$)

Accepted Answer

$$0.50\ \mathrm{mol}$$

Question 18

Which of the following statements about main-group elements is correct?

Accepted Answer

They are found in groups 1, 2, and 13–18 of the periodic table.

Question 19

Which of the following best explains why an $$\mathrm{O}^{2-}$$ ion has a $$2-$$ charge?

Accepted Answer

It has gained two electrons to achieve a stable, noble gas electron configuration.

Question 20

Which of the following best describes the relationship between the electron configuration of an element and its placement in the periodic table?

Accepted Answer

Elements in the same group have similar valence electron configurations, leading to similar chemical properties.

Fundamental Concepts and Atomic Structure in Introduction to Chemistry

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