Question

Valence electrons are those electrons in the outermost principal quantum level (highest \(n\) level) of an atom in its ground state. Groups \(1 \mathrm{A}\) to \(8 \mathrm{A}\) have from 1 to 8 valence electrons. For each group of the representative elements (1A-8A), give the number of valence electrons, the general valence electron configuration, a sample element in that group, and the specific valence electron configuration for that element.

Short answer

Group 1A: 1 valence electron; ns1; Sodium (Na); 3s1. Group 2A: 2 valence electrons; ns2; Magnesium (Mg); 3s2. Group 3A: 3 valence electrons; ns2 np1; Aluminum (Al); 3s2 3p1. Group 4A: 4 valence electrons; ns2 np2; Silicon (Si); 3s2 3p2. Group 5A: 5 valence electrons; ns2 np3; Phosphorus (P); 3s2 3p3. Group 6A: 6 valence electrons; ns2 np4; Sulfur (S); 3s2 3p4. Group 7A: 7 valence electrons; ns2 np5; Chlorine (Cl); 3s2 3p5. Group 8A: 8 valence electrons (except Helium with 2); ns2 np6 (except Helium with 1s2); Neon (Ne); 2s2 2p6.

Step-by-step solution

Group 1A (Alkali Metals)

Number of Valence Electrons: 1 General Valence Electron Configuration: ns1 Sample Element: Sodium (Na) Specific Valence Electron Configuration for Sodium (Na): 3s1

Group 2A (Alkaline Earth Metals)

Number of Valence Electrons: 2 General Valence Electron Configuration: ns2 Sample Element: Magnesium (Mg) Specific Valence Electron Configuration for Magnesium (Mg): 3s2

Group 3A (Boron Group)

Number of Valence Electrons: 3 General Valence Electron Configuration: ns2 np1 Sample Element: Aluminum (Al) Specific Valence Electron Configuration for Aluminum (Al): 3s2 3p1

Group 4A (Carbon Group)

Number of Valence Electrons: 4 General Valence Electron Configuration: ns2 np2 Sample Element: Silicon (Si) Specific Valence Electron Configuration for Silicon (Si): 3s2 3p2

Group 5A (Nitrogen Group)

Number of Valence Electrons: 5 General Valence Electron Configuration: ns2 np3 Sample Element: Phosphorus (P) Specific Valence Electron Configuration for Phosphorus (P): 3s2 3p3

Group 6A (Oxygen Group)

Number of Valence Electrons: 6 General Valence Electron Configuration: ns2 np4 Sample Element: Sulfur (S) Specific Valence Electron Configuration for Sulfur (S): 3s2 3p4

Group 7A (Halogens)

Number of Valence Electrons: 7 General Valence Electron Configuration: ns2 np5 Sample Element: Chlorine (Cl) Specific Valence Electron Configuration for Chlorine (Cl): 3s2 3p5

Group 8A (Noble Gases)

Number of Valence Electrons: 8 (except for Helium, which has 2) General Valence Electron Configuration: ns2 np6 (except for Helium, with configuration 1s2) Sample Element: Neon (Ne) Specific Valence Electron Configuration for Neon (Ne): 2s2 2p6

Key concepts

Principal Quantum Level

Understanding the principal quantum level is essential to grasp how valence electrons behave. Simply put, these levels indicate the energy of an electron within an atom. Think of them like the floors in a hotel: The principal quantum level is denoted by the letter 'n', which can be any whole number starting from 1. As 'n' increases, you're moving to higher floors with more energy.

Valence electrons occupy the outermost floor, or principal quantum level, of an atom. For example, if an electron is in the third principal quantum level, written as 'n=3', it has more energy compared to one at 'n=2'. This is of fundamental importance because the chemical properties of an element are determined by these valence electrons. Valence electrons at a higher 'n' level can be more easily involved in chemical bonds as they are farther away from the positively charged nucleus, and hence less tightly held.

Valence Electron Configuration

Valence electron configuration tells us about the 'address' of an atom's valence electrons. It indicates the types of orbitals these electrons are in, as well as how many electrons are in each type. Orbitals can be thought of as the rooms on each 'floor' of our hotel analogy, where the valence electrons reside.

Representative elements (Groups 1A to 8A) have valence electrons in the 's' and 'p' orbitals. The general configuration is written as 'ns' and 'np', where 'n' is the principal quantum level. In elements from group 1A, which have one valence electron, the configuration is 'ns1'. As we move right in the periodic table, each group adds one more valence electron, leading to 'ns2', 'ns2 np1', and so on until 'ns2 np6' for noble gases (with the exception of helium). The specific configuration of an element includes the actual principal quantum level number, like '2s1' for lithium.

Representative Elements

The term 'representative elements' refers to the main group elements in groups 1A through 8A of the periodic table. These elements display a wide range of physical and chemical properties, and they typically follow the 'rule of eight', referring to the octet rule for filling their valence shells.

Starting from hydrogen and helium and moving down the groups and periods, the number of valence electrons increases from one to eight. This progression corresponds with their group numbers. For instance, group 1A elements have one valence electron, group 2A elements have two, and so forth. Their configurations form patterns: Alkali metals (group 1A) have 'ns1', while the noble gases (group 8A) often have 'ns2 np6', endowing them with unique stability. Understanding these patterns is critical to predicting how elements will react chemically, as valence electrons are key players in chemical reactions.