Chem Unit 2 Review.s25

Which of the following elements is most likely to form a +1 ion?

• Sodium

• Magnesium

• Aluminum

• Silicon

Answer explanation

Sodium is in Group 1 of the periodic table and readily loses one electron to form a +1 ion. In contrast, magnesium, aluminum, and silicon typically form +2, +3, and +4 ions, respectively.

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Predict the relative reactivity of the alkali metals as you move down the group in the periodic table.

• Reactivity decreases

• Reactivity increases

• Reactivity remains the same

• Reactivity first increases then decreases

Answer explanation

As you move down the group of alkali metals, the atomic size increases, leading to a weaker attraction between the outer electron and the nucleus. This results in increased reactivity, making the correct choice 'Reactivity increases'.

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Which element is more electronegative, Fluorine or Chlorine, and why?

• Chlorine, because it has more protons

• Fluorine, because it is smaller in size

• Chlorine, because it is larger in size

• Fluorine, because it has fewer electrons

Answer explanation

Fluorine is more electronegative than Chlorine because it is smaller in size. A smaller atomic radius allows Fluorine to attract electrons more effectively due to its higher effective nuclear charge compared to Chlorine.

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How many valence electrons does Carbon have?

• 2

• 4

• 6

• 8

Answer explanation

Carbon has 4 valence electrons, which are located in its outer shell. This allows it to form four covalent bonds with other atoms, making it a key element in organic chemistry.

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Which of the following elements has the highest ionization energy?

• Lithium

• Beryllium

• Boron

• Helium

Answer explanation

Helium has the highest ionization energy among the given elements due to its small atomic size and full electron shell, making it more difficult to remove an electron compared to lithium, beryllium, and boron.

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• H-O-H with two pairs of dots on O

• H=O=H with no dots

• H-O-H with one pair of dots on O

• H-O-H with three pairs of dots on O

Answer explanation

The correct Lewis dot structure for water (H2O) shows two hydrogen atoms bonded to an oxygen atom. Oxygen has six valence electrons, so it forms two bonds with hydrogen and has two lone pairs, represented as H-O-H with two pairs of dots on O.

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Explain why noble gases are generally unreactive.

• They have a full outer electron shell

• They have an empty outer electron shell

• They have a half-filled outer electron shell

• They have a single electron in their outer shell

Answer explanation

Noble gases are generally unreactive because they have a full outer electron shell. This stable configuration means they do not need to gain, lose, or share electrons, making them less likely to react with other elements.

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Which element is located in period 3, group 16 of the periodic table?

• Sulfur

• Oxygen

• Selenium

• Tellurium

Answer explanation

Sulfur is the element located in period 3, group 16 of the periodic table. Oxygen is in period 2, selenium is in period 4, and tellurium is in period 5, making sulfur the correct choice.

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What is the trend in atomic radius as you move across a period from left to right?

• Increases

• Decreases

• Remains the same

• First increases then decreases

Answer explanation

As you move across a period from left to right, the atomic radius decreases. This is due to the increasing nuclear charge, which pulls the electrons closer to the nucleus, resulting in a smaller atomic size.

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Which of the following elements is a metalloid?

• Silicon

• Sulfur

• Sodium

• Silver

Answer explanation

Silicon is classified as a metalloid due to its properties that are intermediate between metals and nonmetals. Sulfur is a nonmetal, sodium is a metal, and silver is also a metal, making silicon the correct choice.

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