Chemistry · Ch 8 — Elements of Group 1 and 2
Electronic configuration of elements of group 1 and group 2
Electronic configuration of elements of group 1 and group 2
Every group 1 element has the general outer electronic configuration ns¹, and every group 2 element has ns². In both cases these outermost s-electrons are only loosely held by the nucleus and are easily removed, which is exactly why these elements are so chemically reactive that they are never encountered as free, uncombined elements in nature — they are always found already combined in compounds or minerals. Table 8.2 lists the full and condensed electronic configurations for every group 1 element (H through Fr) and Table 8.3 lists the same for every group 2 element (Be through Ra); in every case, removing the outer ns electron(s) leaves an ion — M⁺ for group 1, M²⁺ for group 2 — with the electronic conf …
Table 8.2 — name | symbol | atomic number | condensed configuration | full configuration:
Hydrogen, H, 1, 1s¹, 1s¹.
Lithium, Li, 3, [He] 2s¹, 1s² 2s¹.
Sodium, Na, 11, [Ne] 3s¹, 1s² 2s² 2p⁶ 3s¹.
Potassium, K, 19, [Ar] 4s¹, 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹.
Rubidium, Rb, 37, [Kr] 5s¹, 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s¹.
Caesium, Cs, 55, [Xe] 6s¹, 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s¹. …
Table 8.3 — name | symbol | atomic number | condensed configuration | full configuration:
Beryllium, Be, 4, [He] 2s², 1s² 2s².
Magnesium, Mg, 12, [Ne] 3s², 1s² 2s² 2p⁶ 3s².
Calcium, Ca, 20, [Ar] 4s², 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².
Strontium, symbol Sr (the source prints this as 'St', which is not a real element symbol and is treated here as a printing slip), 38, [Kr] 5s², 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s².
Barium, Ba, 56, [Xe] 6s², 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s². …
Worked out. Worked problem: sodium forms the ionic compounds NaCl, NaH and Na2CO3 — explain. Solution: writing out the charges, these are Na⁺Cl⁻, Na⁺H⁻ and (Na⁺)2CO3²⁻. In every case sodium carries a single positive charge, Na⁺, formed by Na losing one electron: Na → Na⁺ + e⁻. This happens because Na's configuration is [Ne]3s¹ — a single loosely-held electron in the outermost shell that is easily lost, since its ionization enthalpy is low — and because the resulting Na⁺ ion is stable, having the same electronic confi …