Question 1

Which statement about atomic structure is correct according to modern atomic theory?

Accepted Answer

Atoms are composed of protons, neutrons, and electrons, but the atom is the smallest particle that retains the properties of an element.

Question 2

A neutral atom of magnesium-25 ($$\mathrm{Mg}) $$has an atomic number of 12 and a mass number of 25. How many neutrons does it contain?

Accepted Answer

$$13$$

Question 3

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 because additional electron shells are added, increasing the distance from the nucleus.

Question 4

Which element is located in Group 7A, Period 4 of the periodic table?

Accepted Answer

Bromine ($$\mathrm{Br})$$

Question 5

What is the electron configuration for a neutral atom of chlorine ($$\mathrm{Cl}$$, atomic number $$17$$)?

Accepted Answer

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

Question 6

Which of the following elements is classified as a metalloid?

Accepted Answer

Boron ($$\mathrm{B})$$

Question 7

A lead atom ($$\mathrm{Pb}) $$has a mass number of $$207$$ and an atomic number of $$82. $$How many electrons are present in a neutral atom of lead?

Accepted Answer

$$82$$

Question 8

Which of the following statements about ionization energy is correct?

Accepted Answer

Ionization energy increases as you move across a period from left to right.

Question 9

Which element has the highest metallic character among the following?

Accepted Answer

Sodium ($$\mathrm{Na})$$

Question 10

Which of the following is the correct symbol for the isotope of carbon with $$7$$ neutrons?

Accepted Answer

$$^{13}_{6}\mathrm{C}$$

Question 11

If an atom has $$15$$ protons, $$16$$ neutrons, and $$15$$ electrons, what is its atomic number and mass number?

Accepted Answer

Atomic number $$15$$, mass number $$31$$

Question 12

Which of the following best explains why elements in the same group of the periodic table have similar chemical properties?

Accepted Answer

They have the same number of valence electrons.

Question 13

Which element has the largest atomic size: potassium ($$\mathrm{K}) or $$lithium ($$\mathrm{Li}$$)?

Accepted Answer

Potassium ($$\mathrm{K})$$

Question 14

Which element has the higher ionization energy: sulfur ($$\mathrm{S}) or $$silicon ($$\mathrm{Si}$$)?

Accepted Answer

Sulfur ($$\mathrm{S})$$

Question 15

Which of the following is true about the location and charge of subatomic particles in an atom?

Accepted Answer

Protons and neutrons are found in the nucleus; electrons are found outside the nucleus.

Question 16

How many electrons are in the third shell of a neutral atom of calcium ($$\mathrm{Ca}$$, atomic number $$20$$)?

Accepted Answer

$$8$$

Question 17

Which of the following elements is most likely to form a cation by losing one valence electron?

Accepted Answer

Sodium ($$\mathrm{Na})$$

Question 18

Which of the following best describes the relationship between atomic number and the number of protons in an atom?

Accepted Answer

Atomic number is equal to the number of protons.

Question 19

Which of the following elements is a nonmetal?

Accepted Answer

Bromine ($$\mathrm{Br})$$

Question 20

Which of the following best explains why ionization energy decreases as you move down a group in the periodic table?

Accepted Answer

Electrons are further from the nucleus, so less energy is needed to remove them.

Atoms and Electron Energy: Structure, Properties, and Periodic Trends

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