Problem 12 - Chemistry and Chemical Reactivity

Question

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

Step-by-Step Solution

Answer

(a) Pt is an element, Pt(NH3)2Cl2 is a compound. (b) Copper is an element, copper(II) oxide is a compound. (c) Silicon is an element, sand is a compound.

Step 1: Identifying the Element

(a) \ To determine whether \(\mathrm{Pt(NH_3)_2Cl_2}\) or \(\mathrm{Pt}\) is an element or a compound, we need to analyze their chemical composition.\(\mathrm{Pt}\) is a chemical symbol from the periodic table representing one kind of atom, Platinum. Thus, \(\mathrm{Pt}\) is an element. \(\mathrm{Pt(NH_3)_2Cl_2}\), on the other hand, is a chemical formula with Platinum, Nitrogen, Hydrogen, and Chlorine, which makes it a compound.

Step 2: Determining Copper's Nature

(b) \ Copper is represented by the chemical symbol \(\mathrm{Cu}\) and is found on the periodic table, indicating it is an element. Copper(II) oxide is composed of copper (\

Key Concepts

Periodic Table

The periodic table is an essential tool in chemistry, used to organize and display all known chemical elements in a structured way. Each element is represented by a unique chemical symbol, consisting of one or two letters. For example, "Pt" stands for Platinum, and "Cu" represents Copper. Elements are arranged in rows, called periods, and columns, referred to as groups. This organization reveals periodic patterns in the properties of the elements.

By understanding the periodic table, chemists can predict the chemical behavior of an element based on its position. For instance, elements in the same group often exhibit similar reactivity. The table also provides information such as atomic number, which corresponds to the number of protons in an atom's nucleus. Recognizing these patterns is crucial for identifying whether a substance is a pure element or is part of a compound.

Chemical Formulas

Chemical formulas are a shorthand way of representing the composition of compounds. They show the types and numbers of atoms involved in the substance. For example, the chemical formula \(\mathrm{Pt(NH_3)_2Cl_2}\) indicates a compound consisting of ammonium groups and chlorine in addition to platinum atoms. The subscripts in a chemical formula tell us how many atoms of each element are present in the compound.

• "Pt" stands for platinum, an element.
• "NH\(_3\)" represents ammonia, which consists of nitrogen and hydrogen.
• "Cl\(_2\)" refers to chlorine, indicating two chlorine atoms are present.

In contrast, a simple representation like "Cu" or "Si" denotes a pure element with no additional elements combined. Understanding chemical formulas helps us determine the characteristics of compounds, including how they might react chemically. This tool is vital for chemists to understand the composition and properties of different materials.

Element vs Compound Identification

Elements and compounds are fundamental concepts in chemistry, and distinguishing between them is essential. An element is a pure substance that contains only one type of atom. Each element corresponds to a unique symbol and is listed on the periodic table, such as "Pt" for Platinum or "Cu" for Copper.

A compound, on the other hand, comprises two or more different types of atoms chemically bonded together. Compounds can be described using chemical formulas, such as \(\mathrm{CuO}\), which is copper(II) oxide, a combination of copper and oxygen.

• Elements: Pure and single type of atom (e.g., Silicon (Si)).
• Compounds: Combination of different atoms (e.g., sand contains silicon dioxide \(\text{SiO}_2\)).

To identify elements and compounds, look for the chemical symbol or formula. If it represents multiple elements, it's a compound. If it consists of a single element, it is a pure element. This distinction is vital in understanding chemical reactions and material properties.