Chemistry: Periodic Table, Atoms, Molecules, Elements, Mixtures

What is the smallest unit of an element that maintains the properties of that element?

• Molecule

• Atom

• Compound

• Mixture

Answer explanation

The smallest unit of an element that maintains its properties is an atom. Atoms are the building blocks of all matter and cannot be broken down further.

Which of the following is NOT a characteristic of metals on the Periodic Table?

• Conduct electricity

• Are shiny

• Are brittle

• Can be hammered into shapes (malleable)

Answer explanation

The characteristic 'Are brittle' is not associated with metals on the Periodic Table.

How many atoms are in a molecule of water (H2O)?

• 2

• 3

• 4

• 5

Answer explanation

A molecule of water (H2O) consists of 3 atoms: 2 hydrogen atoms and 1 oxygen atom. Therefore, the correct answer is 3.

What distinguishes an element from a compound?

• Elements can be broken down into simpler substances by chemical means.

• Compounds consist of only one type of atom.

• Elements consist of only one type of atom.

• Compounds can exist in any state of matter at room temperature.

Answer explanation

An element consists of only one type of atom, distinguishing it from a compound.

Which of the following is a mixture?

• Water (H2O)

• Salt (NaCl)

• Air

• Gold (Au)

Answer explanation

Air is a mixture because it is composed of different gases, such as nitrogen, oxygen, and carbon dioxide. It is not a pure substance like water or gold.

What is the atomic number of an element?

• The number of protons in the nucleus

• The total number of protons and neutrons in the nucleus

• The number of electrons surrounding the nucleus

• The total mass of the element

Answer explanation

The atomic number of an element is the number of protons in the nucleus, which determines its chemical properties.

Which of the following is true about isotopes?

• They have different numbers of protons.

• They have different numbers of electrons.

• They have different numbers of neutrons.

• They are different elements.

Answer explanation

Isotopes are atoms of the same element with different numbers of neutrons. This distinguishes them from other answer choices.

What type of bond is formed when two atoms share electrons?

• Ionic bond

• Covalent bond

• Metallic bond

• Hydrogen bond

Answer explanation

A covalent bond is formed when two atoms share electrons. This type of bond is characterized by the sharing of electron pairs between atoms, resulting in a stable molecule.

Which group on the Periodic Table is known as the noble gases?

• Group 1

• Group 2

• Group 17

• Group 18

Answer explanation

The noble gases are known as Group 18 on the Periodic Table. They are characterized by their stable and unreactive nature.

What is the term for a substance made of two or more elements that are chemically combined in a fixed ratio?

• Mixture

• Solution

• Compound

• Suspension

Answer explanation

A compound is a substance made of two or more elements that are chemically combined in a fixed ratio.