magnesium vs hydrogen vs potassium vs helium

magnesium (chemical element) | hydrogen (chemical element) | potassium (chemical element) | helium (chemical element)

Periodic table location

Images

| atomic symbol | atomic number | short electronic configuration magnesium | Mg | 12 | [Ne]3s^2 hydrogen | H | 1 | 1s^1 potassium | K | 19 | [Ar]4s^1 helium | He | 2 | 1s^2 | Aufbau diagram | block | group magnesium | 3s | s | 2 hydrogen | 1s | s | 1 potassium | 4s | s | 1 helium | 1s | s | 18 | period | atomic mass | half-life magnesium | 3 | 24.305 u | (stable) hydrogen | 1 | 1.008 u | (stable) potassium | 4 | 39.0983 u | (stable) helium | 1 | 4.002602 u | (stable)

phase at STP | all | gas | solid melting point | median | 63.38 °C | highest | 650 °C (magnesium) | lowest | -259.14 °C (hydrogen) | distribution | boiling point | median | 253 °C | highest | 1090 °C (magnesium) | lowest | -268.93 °C (helium) | distribution | critical temperature | median | 32.97 K | highest | 2223 K (potassium) | lowest | 5.19 K (helium) critical pressure | median | 1.293 MPa | highest | 16 MPa (potassium) | lowest | 0.227 MPa (helium) molar heat of fusion | median | 1.44 kJ/mol | highest | 8.7 kJ/mol (magnesium) | lowest | 0.02 kJ/mol (helium) molar heat of vaporization | median | 38.7 kJ/mol | highest | 128 kJ/mol (magnesium) | lowest | 0.083 kJ/mol (helium) | distribution | specific heat at STP | median | 3106.5 J/(kg K) | highest | 14300 J/(kg K) (hydrogen) | lowest | 757 J/(kg K) (potassium) | distribution | (properties at standard conditions)

density | median | 0.428 g/cm^3 | highest | 1.738 g/cm^3 (magnesium) | lowest | 8.99×10^-5 g/cm^3 (hydrogen) | distribution | molar volume | median | 5630 cm^3/mol | highest | 22420 cm^3/mol (helium) | lowest | 13.98 cm^3/mol (magnesium) | distribution | Brinell hardness | all | 0.363 MPa | 260 MPa Poisson ratio | all | 0.29 sound speed | median | 1600 m/s | highest | 4602 m/s (magnesium) | lowest | 970 m/s (helium) | distribution | thermal conductivity | median | 50 W/(m K) | highest | 160 W/(m K) (magnesium) | lowest | 0.1513 W/(m K) (helium) | distribution | (properties at standard conditions)

valence | median | 1 | highest | 2 (magnesium) | lowest | 0 (helium) | distribution | electronegativity | median | 1.31 | highest | 2.2 (hydrogen) | lowest | 0.82 (potassium) | distribution | electron affinity | median | 24.2 kJ/mol (kilojoules per mole) | highest | 72.8 kJ/mol (kilojoules per mole) (hydrogen) | lowest | 0 kJ/mol (kilojoules per mole) (magnesium and helium) | distribution | first ionization energy | median | 1025 kJ/mol (kilojoules per mole) | highest | 2372.3 kJ/mol (kilojoules per mole) (helium) | lowest | 418.8 kJ/mol (kilojoules per mole) (potassium) | distribution |

term symbol | all | ^1S_0 | ^2S_(1/2) atomic radius | median | 90 pm | highest | 220 pm (potassium) | lowest | 25 pm (hydrogen) | distribution | covalent radius | median | 86 pm | highest | 203 pm (potassium) | lowest | 28 pm (helium) | distribution | van der Waals radius | median | 157 pm | highest | 275 pm (potassium) | lowest | 120 pm (hydrogen) | distribution | (electronic ground state properties)

universe abundance | median | 12 mass% | highest | 75 mass% (hydrogen) | lowest | 3×10^-4 mass% (potassium) solar abundance | median | 12 mass% | highest | 75 mass% (hydrogen) | lowest | 4×10^-4 mass% (potassium) meteorite abundance | median | 2.4 mass% | highest | 12 mass% (magnesium) | lowest | 0.07 mass% (potassium) crust abundance | median | 0.82 mass% | highest | 2.9 mass% (magnesium) | lowest | 5.5×10^-7 mass% (helium) | distribution | ocean abundance | median | 0.086 mass% | highest | 11 mass% (hydrogen) | lowest | 7.2×10^-10 mass% (helium) human abundance | median | 0.2 mass% | highest | 10 mass% (hydrogen) | lowest | 0.027 mass% (magnesium) universe molar abundance | median | 3.6 mol% | highest | 93 mol% (hydrogen) | lowest | 1×10^-5 mol% (potassium) solar molar abundance | median | 3.7 mol% | highest | 93 mol% (hydrogen) | lowest | 9.9×10^-6 mol% (potassium) meteorite molar abundance | median | 10 mol% | highest | 17 mol% (hydrogen) | lowest | 0.037 mol% (potassium) | distribution | ocean molar abundance | median | 0.02 mol% | highest | 66 mol% (hydrogen) | lowest | 1.1×10^-9 mol% (helium) crust molar abundance | median | 1.6 mol% | highest | 3.1 mol% (hydrogen) | lowest | 3×10^-6 mol% (helium) | distribution | human molar abundance | median | 0.032 mol% | highest | 62 mol% (hydrogen) | lowest | 0.007 mol% (magnesium)