Mock Quiz for Chemistry Unit 2.1

Which statement best describes the periodic law?

• Elements with similar properties occur at regular intervals when arranged by atomic mass.

• Elements are arranged in order of increasing atomic number, with repeating patterns in properties.

• Elements with the same number of protons are in the same group.

• Elements with similar chemical properties are placed in the same period.

Answer explanation

The correct statement describes the periodic law accurately, stating that elements are arranged by increasing atomic number, leading to repeating patterns in their properties, which is fundamental to the periodic table.

The concept of "triads" in chemistry, developed by Döbereiner, refers to what?

• Groups of three atoms forming molecules

• Groups of three elements with similar properties

• Groups of three isotopes of the same element

• Groups of three electrons in orbitals

Answer explanation

Döbereiner's concept of "triads" refers to groups of three elements that share similar chemical properties, highlighting the periodic relationships among them. This is why the correct answer is "Groups of three elements with similar properties."

What characteristic increases as you move from left to right across a period?

• Atomic radius

• Metallic character

• Electronegativity

• Ionic radius

Answer explanation

As you move from left to right across a period, electronegativity increases due to the increasing nuclear charge, which attracts electrons more strongly. In contrast, atomic radius and metallic character decrease.

Which group on the periodic table contains elements that exist as diatomic molecules under standard conditions?

• Group 1

• Group 2

• Group 17

• Group 18

Answer explanation

Group 17, known as the halogens, contains elements like F2, Cl2, Br2, and I2, which exist as diatomic molecules under standard conditions. In contrast, Groups 1, 2, and 18 do not primarily form diatomic molecules.

Why do elements in the same group generally have similar chemical properties?

• They have the same atomic mass.

• They have the same number of valence electrons.

• They have the same number of protons.

• They have the same electron configuration.

Answer explanation

Elements in the same group have similar chemical properties because they have the same number of valence electrons. This similarity in valence electrons leads to comparable reactivity and bonding behavior.

Which of the following is true about the alkali metals?

• They have low reactivity.

• They readily form +1 ions.

• They are found in Group 2 of the periodic table.

• They are poor conductors of electricity.

Answer explanation

Alkali metals are highly reactive and readily lose one electron to form +1 ions. They are located in Group 1 of the periodic table, not Group 2, and they are good conductors of electricity.

Transition metals are known for:

• Always having a full outer electron shell.

• Exhibiting a wide range of oxidation states.

• Having low melting points.

• Forming highly reactive compounds with noble gases.

Answer explanation

Transition metals are characterized by their ability to exhibit a wide range of oxidation states due to the involvement of d electrons in bonding. This property allows them to form various compounds and participate in diverse chemical reactions.

Which element is most likely to lose electrons in a chemical reaction?

• Oxygen

• Fluorine

• Potassium

• Sulfur

Answer explanation

Potassium is an alkali metal, known for its tendency to lose one electron easily during chemical reactions, forming positive ions. In contrast, oxygen, fluorine, and sulfur are more likely to gain electrons.

How do noble gases differ from most other elements?

• They are highly reactive due to their filled valence shell.

• They do not form bonds easily because they have a full valence shell.

• They are the most abundant elements in the Earth's crust.

• They easily lose electrons in reactions.

Answer explanation

Noble gases have a full valence shell, making them stable and unreactive. This is why they do not form bonds easily, unlike most other elements that seek to fill their valence shells through bonding.

Which of the following is a metalloid?

• Argon

• Carbon

• Boron

• Sodium

Answer explanation

Boron is classified as a metalloid due to its properties that are intermediate between metals and nonmetals. Argon is a noble gas, carbon is a nonmetal, and sodium is a metal, making boron the correct choice.