Question

What is the group number and number of valence electrons for each of the following elements? a. magnesium b. chlorine c. oxygen d. nitrogen e. barium f. bromine

Short answer

Mg: Group 2, 2 valence e−; Cl: Group 17, 7 valence e−; O: Group 16, 6 valence e−; N: Group 15, 5 valence e−; Ba: Group 2, 2 valence e−; Br: Group 17, 7 valence e−.

Step-by-step solution

Identify Magnesium (Mg)

Look up magnesium (Mg) in the periodic table. It is located in Group 2 and has 2 valence electrons.

Identify Chlorine (Cl)

Look up chlorine (Cl) in the periodic table. It is located in Group 17 and has 7 valence electrons.

Identify Oxygen (O)

Look up oxygen (O) in the periodic table. It is located in Group 16 and has 6 valence electrons.

Identify Nitrogen (N)

Look up nitrogen (N) in the periodic table. It is located in Group 15 and has 5 valence electrons.

Identify Barium (Ba)

Look up barium (Ba) in the periodic table. It is located in Group 2 and has 2 valence electrons.

Identify Bromine (Br)

Look up bromine (Br) in the periodic table. It is located in Group 17 and has 7 valence electrons.

Key concepts

Valence Electrons

Valence electrons are the outermost electrons of an atom. They play a crucial role in chemical reactions because they can be lost, gained or shared to form chemical bonds.

Atoms within the same column in the periodic table have similar valence electron configurations.

• Having similar valence electron configurations makes their chemical properties comparable.
• For example, all Group 1 elements have 1 valence electron.
• Understanding valence electrons helps predict how elements interact with each other.

Element Groups

Elements in the periodic table are arranged in columns known as groups. Each group contains elements with similar properties. Groups are numbered from 1 to 18.

• Group 1: Alkali metals like lithium and sodium.
• Group 2: Alkaline earth metals such as magnesium and calcium.
• Groups 3 to 12: Transition metals including iron and copper.
• Group 17: Halogens like chlorine and bromine.
• Group 18: Noble gases such as helium and neon.

Knowing the group number helps predict the number of valence electrons each element has.

Magnesium

Magnesium is an alkaline earth metal found in Group 2 of the periodic table. It is represented by the symbol Mg.

Magnesium has 2 valence electrons.

• Its valence electrons are in the s-orbital.
• Because it has only 2 valence electrons, magnesium easily loses them to form a Mg²⁺ ion.
• It is frequently used in alloys and as a reducing agent in chemical reactions.

Chlorine

Chlorine is a halogen located in Group 17 of the periodic table. Its symbol is Cl.

Chlorine has 7 valence electrons.

• These electrons are in the p-orbital.
• Lacking one electron to complete its valence shell, chlorine readily gains an electron to form a Cl^- ion.
• It is commonly used for disinfection and in the production of PVC plastics.

Oxygen

Oxygen is found in Group 16 of the periodic table and is represented by the symbol O.

Oxygen has 6 valence electrons.

• These valence electrons enable oxygen to form two covalent bonds.
• Oxygen is essential for respiration in most life forms and is often found in water (H₂O).
• It is highly reactive and readily forms oxides with most elements.

Nitrogen

Nitrogen is a Group 15 element and has the symbol N.

Nitrogen has 5 valence electrons.

• These electrons allow nitrogen to form three covalent bonds.
• It is a primary component of the Earth's atmosphere.
• Nitrogen is crucial for the production of amino acids and proteins in living organisms.

Barium

Barium is an alkaline earth metal in Group 2, symbolized as Ba.

Barium has 2 valence electrons.

• These electrons are in the s-orbital and it often loses them to form Ba²⁺ ions.
• Barium is used in x-ray imaging, fireworks, and as a getter in vacuum tubes.

Bromine

Bromine is a halogen in Group 17, represented by the symbol Br.

Bromine has 7 valence electrons.

• These electrons are in the p-orbital.
• Bromine commonly gains an electron to form a Br^- ion.
• It is used in flame retardants and certain types of medication.