Problem 6 - Chemistry and Chemical Reactivity

Question

In each of the following pairs, decide which is an element and which is a compound. (a) \(\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\) and \(\mathrm{Pt}\) (b) copper or copper(II) oxide (c) silicon or sand

Step-by-Step Solution

Answer

(a) Pt(NH3)2Cl2 is a compound; Pt is an element. (b) Copper(II) oxide is a compound; copper is an element. (c) Sand is a compound; silicon is an element.

Step 1: Identifying Elements and Compounds: Pt(NH3)2Cl2 vs Pt

Platinum dichloride diamine, represented as \( \text{Pt}(\text{NH}_3)_2 \text{Cl}_2 \), is composed of one platinum atom, two ammonia molecules, and two chlorine atoms, making it a combination of different elements. Therefore, it is a compound. On the other hand, \( \text{Pt} \) represents pure platinum, which is a single type of atom, hence an element.

Step 2: Identifying Elements and Compounds: Copper vs Copper(II) Oxide

Copper(II) oxide is a chemical compound represented as \( \text{CuO} \), which consists of copper and oxygen atoms. Since it contains more than one type of element, it is a compound. Copper alone, on the other hand, is made purely of copper atoms, making it an element.

Step 3: Identifying Elements and Compounds: Silicon vs Sand

Silicon is a pure chemical element with the symbol \( \text{Si} \), consisting of only silicon atoms. Sand, however, is primarily composed of silicon dioxide \( \text{SiO}_2 \), which is a compound as it consists of silicon and oxygen atoms bound together.

Key Concepts

Chemical Compounds

Chemical compounds are substances made up of two or more different types of elements. They are formed by chemical bonds that join different atoms together. This combination allows compounds to have distinct properties different from the individual elements they are composed of.

• A common example is water (\( \text{H}_2\text{O} \)), which is a compound formed from hydrogen and oxygen.
• Another example is sodium chloride (\( \text{NaCl} \)), a compound made from sodium and chlorine.

Chemical compounds can vary widely in their complexity:

• Simple compounds like carbon dioxide (\( \text{CO}_2 \)) consist of only three atoms.
• More complex compounds like proteins contain thousands of atoms.

Understanding compounds helps us grasp how elements interact to form diverse materials across the universe.

Chemical Elements

Chemical elements are pure substances consisting of only one type of atom. These elements are the basic building blocks of matter and are organized in the periodic table.
They are characterized by a specific number of protons in their atomic nuclei, known as the atomic number.

• Examples include hydrogen (\( \text{H} \)), which is the simplest element with an atomic number of 1.
• Iron (\( \text{Fe} \)) is another element, characterized by its metallic properties.

Each element has unique chemical and physical properties:

• The metal copper (\( \text{Cu} \)) conducts electricity efficiently.
• The non-metal oxygen (\( \text{O} \)) is vital for respiration.

By understanding chemical elements, we can better understand the materials around us and their interactions.

Chemical Nomenclature

Chemical nomenclature is the system used to name chemical substances. It helps scientists and students identify compounds based on their composition and structure. This system is essential for clear communication in the scientific community.

• For compounds, the nomenclature often includes the names of the elements involved and numerical prefixes that convey how many atoms of each element are present.
• An example is carbon monoxide (\( \text{CO} \)), indicating one carbon atom and one oxygen atom.

Naming compounds accurately is critical for avoiding confusion:

• Copper(II) oxide (\( \text{CuO} \)) clearly indicates the oxidation state of copper.
• For molecular compounds, the prefixes \( \ ext{di-}=2,\ \ ext{tri-}=3 \) are used to indicate the number of each type of atom.

By mastering chemical nomenclature, students can easily interpret chemical formulas and communicate their findings effectively.