Group 18 elements are known as noble gases or inert gases. They possess a full valence shell (eight electrons, except for helium which has two), making them chemically stable and largely unreactive under standard conditions. This electronic configuration results in very high ionization energies and low electron affinities, distinguishing them from other groups in the periodic table.

Electronegativity decreases down a group because the atomic radius increases, leading to a greater distance between the nucleus and the valence electrons, which reduces the effective attraction for shared electrons.

Metallic character increases down a group because the ionization energy decreases as the valence electron is further from the nucleus. For Group 1 elements, the metallic character increases in the order Li < Na < K < Rb < Cs, as the atomic size increases and the outer electron is more easily lost.

Elements in the same group of the periodic table share the same number of valence electrons. This similarity in electronic configuration is the primary reason why elements in the same group exhibit similar chemical properties.

Metallic character increases as you move from right to left across a period and from top to bottom down a group. Rubidium (Rb) is an alkali metal located in Group 1 of the fifth period. As an alkali metal, it has the lowest ionization energy in its period, making it the most electropositive and thus the most metallic element in that row of the periodic table.

Statement 1 is generally accepted as reactivity decreases toward the middle of a period and increases toward the ends. Statement 2 is false because non-metal reactivity decreases down a group due to increased atomic size and decreased electron affinity, making it harder to attract electrons.

The electronic configuration 2, 8, 6 indicates a total of 16 electrons, identifying the element as Sulfur. The number of valence electrons is 6. In the modern periodic table, elements with 6 valence electrons belong to Group 16 (the oxygen family), as the group number for p-block elements is calculated as 10 + valence electrons.

Periodic properties are those that repeat at regular intervals as atomic number increases. Atomic size, electronegativity, and ionization energy show clear periodic trends. The neutron-to-proton ratio is a nuclear property related to isotopic stability rather than a periodic trend of chemical behavior in the periodic table.

Non-metallic character increases as you move from left to right across a period in the periodic table. Sodium (Na) is an alkali metal, while Chlorine (Cl) is a halogen. As you move from Na to Cl across the third period, the atomic radius decreases and the effective nuclear charge increases, making it easier for the elements to gain electrons, thereby increasing their non-metallic properties.

Group 18 elements, known as noble gases, have a stable electronic configuration with a full valence shell (ns2 np6, except for Helium which is 1s2). This complete octet or duplet configuration makes them chemically inert under standard conditions, as they have little tendency to gain, lose, or share electrons.