Problem 5 - Chemistry and Chemical Reactivity

Question

In each of the following pairs, decide which is an element and which is a compound. (a) \(\mathrm{Na}\) and \(\mathrm{NaCl}\) (b) sugar and carbon (c) gold and gold chloride

Step-by-Step Solution

Answer

(a) Na is an element, NaCl is a compound; (b) carbon is an element, sugar is a compound; (c) gold is an element, gold chloride is a compound.

Step 1: Understand Elements

Elements are pure substances made of only one type of atom. They are listed in the periodic table, such as sodium (Na) and carbon (C).

Step 2: Understand Compounds

Compounds are substances formed when two or more different elements are chemically bonded. For example, sodium chloride (NaCl) is a compound composed of sodium and chlorine atoms.

Step 3: Analyze Pair (a)

The first pair is sodium (Na) and sodium chloride (NaCl). Sodium is an element because it consists of only one type of atom. Sodium chloride is a compound because it is made from sodium and chlorine atoms chemically bonded together.

Step 4: Analyze Pair (b)

The second pair is sugar and carbon. Carbon is an element because it's composed of only one type of atom. Sugar is a compound because it consists of carbon, hydrogen, and oxygen atoms bonded together.

Step 5: Analyze Pair (c)

The third pair is gold and gold chloride. Gold is an element since it consists of only one type of atom. Gold chloride, however, is a compound because it contains gold and chlorine atoms bonded.

Key Concepts

Elements

Elements are the building blocks of matter. They are pure substances that consist of only one type of atom. Think of elements as the simplest forms of substances you can find. If you take a piece of gold (\(\text{Au}\)), it is purely made of gold atoms and nothing else. Elements are identified by unique symbols and are ordered in the periodic table based on their atomic number, which is the number of protons in their nucleus. For a student learning chemistry, it's essential to know that each element has its own distinct set of properties that can be understood through this table.

• Examples of elements: oxygen (\(\text{O}\)), hydrogen (\(\text{H}\)), and sodium (\(\text{Na}\)).
• Elements can exist in different states like solid, liquid, or gas at room temperature.

Remember, elements cannot be broken down into simpler substances by chemical means.

Compounds

While elements are made of single types of atoms, compounds are substances formed when two or more different types of atoms bond together. This bonding results in a completely new substance with properties distinct from its constituent elements. For instance, sodium (an element that reacts vigorously with water) combines with chlorine (\(\text{Cl}\)), a toxic gas, to form sodium chloride (\(\text{NaCl}\)), or common table salt, which is safe to consume.

• Compounds have a fixed composition, defined by a specific chemical formula.
• The properties of compounds differ from the properties of the individual elements that make them up.

In chemical reactions, the individual atoms that constitute a compound are rearranged to form new compounds, showcasing the dynamic nature of chemical bonds.

Periodic Table

The periodic table is a crucial tool in chemistry. It organizes all known elements in an informative grid based on increasing atomic number, electron configuration, and recurring chemical properties. This arrangement helps predict the behavior of elements and the types of chemical bonds they can form. The table divides elements into categories such as metals, nonmetals, and metalloids, which helps simplify understanding complex chemical behaviors.

• Groups or families are vertical columns in the table, and elements within the same group exhibit similar properties.
• Periods are horizontal rows, and moving across a period shows a progression of elements with incrementally increasing atomic numbers.

By knowing an element's position in the periodic table, students can infer its properties, predict how it will react with other substances, and understand the compound formation.

Chemical Bonds

Chemical bonds are the forces holding atoms together in compounds. They form because atoms seek to attain a stable electron configuration similar to the nearest noble gas, achieving a state of lower energy. The main types of chemical bonds are ionic bonds and covalent bonds.

• Ionic bonds occur when electrons are transferred from one atom to another, resulting in oppositely charged ions that attract each other. An example is sodium donating an electron to chlorine, forming sodium chloride (\(\text{NaCl}\)).
• Covalent bonds involve the sharing of electron pairs between atoms, as seen in molecules like water (\(\text{H}_2 ext{O}\)).

Understanding how these bonds work and their impact on the resulting compounds is fundamental for grasping more advanced chemistry concepts. Bonds determine the structure, shape, and properties of compounds, influencing how they interact with other substances.