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) Carbon (C), (b) Rubidium (Rb), (c) Chlorine (Cl), (d) Oxygen (O)

Step-by-step solution

Identify Nonmetals in the Second Period

The second period elements include lithium (Li) through neon (Ne). Nonmetals in this period are boron (B), carbon (C), nitrogen (N), oxygen (O), fluorine (F), and neon (Ne).

Select the Alkali Metal in the Fifth Period

Alkali metals belong to Group 1 of the periodic table. The fifth period starts with rubidium (Rb) and includes rubidium (Rb), strontium (Sr), and other elements. The alkali metal is rubidium (Rb).

Find the Halogen in the Third Period

Halogens are in Group 17 of the periodic table. The third period includes sodium (Na) through argon (Ar). The halogen in the third period is chlorine (Cl).

Identify Elements that are Gases at Room Temperature and Pressure

Common gaseous elements at room temperature include hydrogen (H), nitrogen (N), oxygen (O), fluorine (F), chlorine (Cl), and noble gases like helium (He), neon (Ne), and argon (Ar).

Key concepts

Chemical Symbols

A chemical symbol is a shorthand way to represent a chemical element using one or two letters. These letters are often derived from the element's name in English, Latin, or another language. For example, the symbol for oxygen is \( O \), while the symbol for gold is \( Au \), derived from the Latin word "aurum."

Chemical symbols are universally recognized, making communication clearer and simpler across different languages and regions. They are essential when writing chemical equations and formulas. For instance, in the chemical equation \( 2H_2 + O_2 ightarrow 2H_2O \), the symbols \( H \) and \( O \) represent hydrogen and oxygen. This allows chemists to understand what elements are involved and their proportions in reactions.

• Each element in the periodic table is assigned a unique chemical symbol.
• Symbols are capitalized with a lowercase second letter if present, such as \( Fe \) for iron.
• Having a firm grasp on chemical symbols helps in exploring the periodic table effectively.

Alkali Metals

Alkali metals are a group of chemical elements in Group 1 of the periodic table. These elements are highly reactive metals and include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Due to their single electron in the outermost energy level, they readily lose this electron to form positive ions.

The reactivity of alkali metals increases as you move down the group, meaning rubidium is more reactive than sodium. Their reactivity also makes them excellent conductors of electricity. However, their high reactivity requires careful handling and storage.

• Alkali metals are soft and can be cut with a knife.
• They have low melting points compared to most metals.
• Rubidium (Rb), found in the fifth period, is one such alkali metal.

Halogens

Halogens belong to Group 17 of the periodic table and include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). These elements are highly reactive nonmetals, mainly because they are just one electron short of a complete valence shell. This means they easily form negative ions and compounds, especially salts with alkali metals.

Chlorine (Cl), for example, is the halogen in the third period. It is commonly used for water purification and in bleach. The reactivity of halogens decreases as you move down the group.

• Halogens form salts when reacting with metals, such as sodium chloride (table salt).
• They have varied states at room temperature: fluorine and chlorine are gases, bromine is a liquid, while iodine and astatine are solids.
• Have crucial uses in everyday life, ranging from disinfectants to medicine.

Gaseous Elements

The periodic table contains several elements that exist as gases at room temperature and normal atmospheric pressure. These include hydrogen (H), nitrogen (N), oxygen (O), fluorine (F), chlorine (Cl), and the noble gases: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).

Gaseous elements play vital roles in natural and industrial processes. Oxygen, for instance, is essential for life as it is a critical component of the air we breathe, while nitrogen is used in fertilizers to enhance plant growth.

• Gaseous elements do not have a fixed shape or volume, and they expand to fill any container.
• Noble gases are inert, meaning they are very stable and do not react readily with other elements.
• These gases are vital for life and technology, including breathing, lighting, and welding.