Question

Give the name and chemical symbol for the following. (a) a nonmetal in the second period (b) an alkali metal in the fifth period (c) the third-period halogen (d) an element that is a gas at \(20^{\circ} \mathrm{C}\) and 1 atmosphere pressure

Short answer

(a) N/F/O/Ne, (b) Rb, (c) Cl, (d) H/N/O/F/Ne/Cl/Ar.

Step-by-step solution

Identify a Nonmetal in the Second Period

In the periodic table, the second period consists of elements with atomic numbers 3 to 10. The nonmetals in this period are nitrogen (N), oxygen (O), fluorine (F), and neon (Ne). The nonmetal element names and symbols are: - Nitrogen: N - Oxygen: O - Fluorine: F - Neon: Ne. Choose one based on other given conditions or list them all if not specified.

Identify an Alkali Metal in the Fifth Period

Alkali metals are found in group 1 of the periodic table. The fifth period has elements with atomic numbers 37 to 54. Among these, the only alkali metal is rubidium (Rb). Thus, the alkali metal in the fifth period is rubidium (Rb).

Find the Third-Period Halogen

Halogens are located in group 17 of the periodic table. In the third period, elements have atomic numbers 11 to 18. The halogen in this period is chlorine (Cl). So, the third-period halogen is chlorine (Cl).

Determine an Element that is a Gas at 20°C and 1 atm

Common gases at room temperature and pressure include hydrogen (H), nitrogen (N), oxygen (O), fluorine (F), neon (Ne), chlorine (Cl), and argon (Ar). Choose one of these gases, as the question does not specify any other criteria.

Key concepts

Nonmetals

Nonmetals are a fascinating group of elements found on the right side of the periodic table. They are distinct from metals due to their varied appearances and lack of metallic luster. Nonmetals play crucial roles in everyday life as they are essential for various biological and chemical processes.
Nonmetals gain electrons during chemical reactions and are usually poor conductors of heat and electricity. They can be solid, liquid, or gas at room temperature.
In the second period of the periodic table, the nonmetals include:

• Nitrogen (N): A gas that makes up about 78% of the Earth's atmosphere. It is vital for the synthesis of proteins and nucleic acids in living organisms.
• Oxygen (O): Another gas that is crucial for life, supporting respiration in aerobic organisms and making up 21% of the atmosphere.
• Fluorine (F): A highly reactive gas at room temperature, used in toothpaste and Teflon production.
• Neon (Ne): An inert gas, often used in lighting and advertising signs.

These nonmetals all share the common trait of completing their outer electron shell during reactions by gaining electrons.

Alkali Metals

Alkali metals are located in Group 1 of the periodic table. This group is characterized by its high reactivity and includes lithium, sodium, potassium, rubidium, cesium, and francium. These metals are soft, shiny, and have a silvery appearance. They have one electron in their outermost shell, which they readily lose to form positive ions or cations.
In the fifth period, the alkali metal is rubidium (Rb). This metal:

• Is highly reactive, especially with water, forming alkaline hydroxides.
• Combines with halogens, oxygen, and other nonmetals in various compounds.
• Is used in research and specialized applications, such as atomic clocks.

Alkali metals are never found in a free state in nature due to their high reactivity.

Halogens

Halogens are found in Group 17 of the periodic table and are known for their strong ability to react, particularly with metals to form salts. The word "halogen" comes from Greek and means "salt-former." The halogens include fluorine, chlorine, bromine, iodine, and astatine. They have seven electrons in their outermost shell, making them highly reactive as they seek to gain one electron to achieve a full octet.
In the third period, chlorine (Cl) is the halogen present.

• Chlorine is a yellow-green gas with a strong odor, widely used in disinfection and the production of various chlorides, including common table salt (sodium chloride).
• It plays a significant role in maintaining public health through water treatment.

Halogens often form acids when combined with hydrogen and are crucial in organic chemistry and pharmaceuticals.

Gaseous Elements

At room temperature and standard atmospheric pressure, certain elements naturally exist as gases. This state of matter is characterized by the fast movement and wide spacing of molecules, leading to low density and the ability to fill any container.

• Hydrogen (H): The lightest and most abundant element in the universe, primarily found in stars and interstellar spaces.
• Nitrogen (N): Dominates Earth's atmosphere and is crucial for life, being a fundamental component of amino acids and nucleic acids.
• Oxygen (O): Essential for respiration, it also supports combustion and is highly reactive.
• Fluorine (F) and Chlorine (Cl): Both are reactive halogen gases used in many industrial processes.
• Neon (Ne) and Argon (Ar): Inert gases mainly used in lighting and welding due to their chemical inertness.

These gases have diverse applications, from supporting life to industrial uses, driven by their unique properties.