Question

Identify the following elements. (a) A member of the same period as tellurium but with three fewer protons than tellurium. (b) A post-transition metal in Group 14 (c) An alkali with 19 protons (d) A metalloid in Group 15 with more than 40 protons

Short answer

Question: Identify the following elements: (a) The element in the same period as tellurium with three fewer protons. (b) A post-transition metal in Group 14. (c) An alkali metal with 19 protons. (d) A metalloid in Group 15 with more than 40 protons. Answer: (a) Indium (In) (b) Tin (Sn) or Lead (Pb) (c) Potassium (K) (d) Antimony (Sb)

Step-by-step solution

(a) Identify the element in the same period as tellurium with three fewer protons

First, locate tellurium (Te) in the periodic table, which is in period 5 and group 16. Te has an atomic number of 52, which means it has 52 protons. To find an element with three fewer protons, subtract 3 from 52, which gives us 49. The element with 49 protons is Indium (In), which is also located in period 5.

(b) Identify a post-transition metal in Group 14

Locate Group 14 on the periodic table, which includes carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). The post-transition metals are the metallic elements in this group below the metalloid germanium. Thus, the post-transition metals in Group 14 are tin (Sn) and lead (Pb).

(c) Identify an alkali metal with 19 protons

The alkali metals are located in Group 1 of the periodic table. To find an alkali metal with 19 protons, search for an element in Group 1 with an atomic number of 19. The element with 19 protons is potassium (K), which is also an alkali metal.

(d) Identify a metalloid in Group 15 with more than 40 protons

Locate Group 15 on the periodic table, which includes nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). The metalloid in Group 15 is arsenic (As). It has 33 protons, which is less than 40 protons. The next element in Group 15 is antimony (Sb), which has 51 protons. Antimony (Sb) is also considered a metalloid and has more than 40 protons, making it the answer.

Key concepts

Periods and Groups in the Periodic Table

Understanding the layout of the periodic table is crucial to identifying elements and their properties. The periodic table is divided into horizontal rows known as periods and vertical columns referred to as groups or families.

Periods are numbered from 1 to 7 and indicate the number of electron shells an element possesses. As you move across a period from left to right, the atomic number increases, and elements gain more protons and electrons. At the end of each period, you find noble gases, renowned for their stability and lack of reactivity due to having a full outer electron shell.

Groups, on the other hand, range from 1 to 18 (in some classifications, they are numbered from 1A to 8A and then from 1B to 8B, excluding the transition metals) and contain elements with similar chemical properties. For instance, group 1 houses the alkali metals, which are highly reactive due to having a single electron in their outermost shell. Recognizing the positioning of periods and groups eases the process of identifying elements, such as the one in period 5 with an atomic number of 49, which is Indium (In).

Post-Transition Metals

Post-transition metals are located on the periodic table to the right of the transition metal block and to the left of the metalloids. They're generally softer and have lower melting points than transition metals, and they're also less conductive.

In Group 14, the post-transition metals include tin (Sn) and lead (Pb), which lie below the metalloid germanium (Ge). These metals are known for their malleability and are often used in alloys and other industrial applications. For example, lead has been used historically in pipes and paint, although its use has declined due to health concerns. Tin, on the other hand, is commonly used to coat other metals to prevent corrosion. Identifying post-transition metals helps one understand their unique features in comparison to the rest of the periodic table.

Alkali Metals

The alkali metals form Group 1 of the periodic table and are known for being highly reactive, particularly with water. They are characterized by having a single valence electron, which they readily lose to form positive ions, known as cations.

Each period (with the exception of the first) features one alkali metal, starting with lithium (Li), sodium (Na), and moving down to francium (Fr). The given example of an element in this group with 19 protons is potassium (K). It is used in various industries and biological processes, including as a nutrient in agriculture and a critical electrolyte in the human body. The reactivity of alkali metals increases as you move down the group, which is why proper handling and understanding of these metals are essential in both chemical and real-world applications.

Metalloid Properties

Metalloids are fascinating elements that exhibit properties intermediate between those of metals and non-metals. Located on the periodic table along the staircase-like line starting at boron (B) and extending down to astatine (At), metalloids have a unique set of characteristics.

They can generally conduct electricity better than non-metals but not as well as metals, making them excellent semiconductors. This quality is integral to modern electronics, including computers and smartphones. Metalloids such as silicon (Si) dominate the technology industry for this reason.

When identifying metalloids in Group 15 with more than 40 protons, for example, antimony (Sb) is the answer. Metalloids like antimony are utilized in alloys, flame retardants, and even in some medications. Understanding metalloid properties helps us appreciate their versatility and essential role in technological advancement.