Question

State the number of valence electrons in each of the following groups as predicted from the periodic table: (a) Group IIA/2 (b) Group IVA/14 (c) Group VIA/16 (d) Group VIIIA/18

Short answer

(a) 2 electrons, (b) 4 electrons, (c) 6 electrons, (d) 8 electrons

Step-by-step solution

Understanding Group Notation

In the periodic table, the groups are the columns numbered from 1 to 18. The Roman numeral along with the letter 'A' refers to the main group elements. Each group has a characteristic number of valence electrons that determine the chemical properties of the elements.

Determine Valence Electrons in Group IIA/2

Elements in Group IIA/2 include beryllium, magnesium, calcium, etc. These elements have the outer electron configuration ending in 's', specifically 's^2'. Therefore, each element in Group IIA/2 has 2 valence electrons.

Determine Valence Electrons in Group IVA/14

Group IVA/14 includes carbon, silicon, germanium, etc. The outer electron configuration of these elements ends in 's^2 p^2', giving a total of 4 valence electrons for each element in this group.

Determine Valence Electrons in Group VIA/16

Elements found in Group VIA/16, such as oxygen and sulfur, have the outer electron configuration ending in 's^2 p^4'. Therefore, each element in Group VIA/16 has 6 valence electrons.

Determine Valence Electrons in Group VIIIA/18

Group VIIIA/18 includes the noble gases, such as helium, neon, and argon. With the exception of helium, which has 2 valence electrons, other noble gases have a full outer electron configuration of 's^2 p^6', totaling 8 valence electrons.

Key concepts

Periodic Table

The periodic table is a fundamental tool in chemistry and is structured in such a way that it reveals a lot about the elements it classifies. One of its most important features is that it organizes elements by increasing atomic number, which is the number of protons in an atom's nucleus.

Additionally, the periodic table is divided into rows called periods and columns known as groups. These groups can tell us a lot about the chemical behavior of the elements within them.

Elements are grouped based on similar properties and the number of valence electrons they possess. Valence electrons are those electrons located in the outermost shell of an atom; they play the primary role in chemical bonding and reactions.

• Groups: Vertical columns numbered from 1 to 18.
• Periods: Horizontal rows that represent energy levels of electrons.
• Main Group Elements: Consist of Groups 1-2 and 13-18.

Understanding the layout of the periodic table allows chemists to predict numerous properties of the elements, including their valence electrons. This is fundamental in predicting how different elements will interact in chemical reactions.

Main Group Elements

Main group elements are those found in Groups 1, 2, and 13 to 18 of the periodic table. These elements are significant because they include many of the most common elements encountered in everyday life, such as hydrogen, carbon, oxygen, and the elements forming the noble gases.

A characteristic feature of main group elements is how their valence electrons are arranged. The number of valence electrons determines an element's chemical properties and reactivity. Here's a breakdown of the number of valence electrons in each main group under standard conditions:

• Group 1 (IA): Having 1 valence electron, making them highly reactive.
• Group 2 (IIA): Featuring 2 valence electrons, typical of alkaline earth metals.
• Group 13 (IIIA): Containing 3 valence electrons.
• Group 14 (IVA): With 4 valence electrons, including the element carbon, which is essential for life.
• Group 15 (VA): Consist of 5 valence electrons.
• Group 16 (VIA): Known as chalcogens, they possess 6 valence electrons.
• Group 17 (VIIA): Called halogens, these have 7 valence electrons and are highly reactive.
• Group 18 (VIIIA): Noble gases, generally having 8 valence electrons, making them mostly inert.

These valence electrons are crucial for the formation of chemical bonds, and thus, understanding these groups helps in predicting how elements will interact.

Electron Configuration

Electron configuration is a way to represent the distribution of electrons around the nucleus of an atom. This distribution affects the way an element behaves in chemical reactions.

Each element's electron configuration is unique and is typically written using a notation that denotes the energy level (n), the type of orbital (s, p, d, f), and the number of electrons in those orbitals, such as 1s² for helium.

The main points to grasp concerning electron configurations include:

• For main group elements, the outermost s and p orbitals hold the valence electrons.
• The s orbital can hold a maximum of 2 electrons, while the p orbital can hold up to 6.
• Electron configurations provide insights into an atom's reactivity, giving clues about potential chemical bonds.
• Atoms tend to seek a stable electron configuration, typically one resembling the nearest noble gas, explaining trends like what creates bonds in ionic and covalent compounds.

By understanding electron configurations, one can predict various chemical properties and behaviors, including understanding why Group IIA elements like magnesium have 2 valence electrons and how this affects their potential as reducing agents in reactions.