chemical element, or element, is a type of atom that is defined by its atomic number; that is, by the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.
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Periods:]] 1 2 3 4 5 6 7 8
Series Alkalis Alkaline earths Lanthanides Actinides Transition metals Poor metals Metalloids Nonmetals Halogens Noble gases
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The periodic table of the chemical elements is a tabular method of displaying the chemical elements. Although precursors to this table exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869.
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The lanthanide (or lanthanoid) series comprises the 15 elements with atomic numbers 57 through 71, from lanthanum to lutetium^[1]. All lanthanides are f-block elements, corresponding to the filling of the 4f electron shell, except for lutetium which is a d-block
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A group, also known as a family, is a vertical column in the periodic table of the chemical elements. There are 18 groups in the standard periodic table.

The modern explanation of the pattern of the periodic table is that the elements in a group have similar
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The alkaline earth metals are a series of elements comprising Group 2 (IUPAC style) of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra).
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Caesium (also spelled cesium, IPA: /ˈsiːziəm/) is a chemical element in the periodic table that has the symbol Cs and atomic number 55.
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Barium (IPA: /ˈbɛːɹiəm/) is a chemical element. It has the symbol Ba, and atomic number 56. Barium is a soft silvery metallic alkaline earth metal.
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Hafnium (IPA: /ˈhæfniəm/) is a chemical element that has the symbol Hf and atomic number 72. A lustrous, silvery gray tetravalent transition metal, hafnium resembles zirconium chemically and it is found in
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5, 4, 3 (mildly acidic oxide)
Electronegativity 1.5 (scale Pauling)
Ionization energies 1st: 761 kJ/mol
2nd: 1500 kJ/mol
Atomic radius 145 pm
Atomic radius (calc.
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6, 5, 4, 3, 2, 1, 0, −1
(mildly acidic oxide)
Electronegativity 2.36 (scale Pauling)
Ionization energies 1st: 770 kJ/mol
2nd: 1700 kJ/mol
Atomic radius 135 pm
Atomic radius (calc.
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7, 6, 5, 4, 3, 2, 1, −1, −2, −3
(mildly acidic oxide)
Electronegativity 1.9 (scale Pauling)
Ionization energies
(more) 1st: 760 kJmol⁻¹
2nd: 1260 kJmol⁻¹
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4, 3, 2, 1, −1, −2
(mildly acidic oxide)
Electronegativity 2.2 (scale Pauling)
Ionization energies 1st: 840 kJ/mol
2nd: 1600 kJ/mol
Atomic radius 130 pm
Atomic radius (calc.
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4, 6
(mildly basic oxide)
Electronegativity 2.20 (scale Pauling)
Ionization energies 1st: 880 kJ/mol
2nd: 1600 kJ/mol
Atomic radius 135 pm
Atomic radius (calc.
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4, 5, 6
(mildly basic oxide)
Electronegativity 2.28 (scale Pauling)
Ionization energies 1st: 870 kJ/mol
2nd: 1791 kJ/mol
Atomic radius 135 pm
Atomic radius (calc.
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GOLD refers to one of the following:

• GOLD (IEEE) is an IEEE program designed to garner more student members at the university level (Graduates of the Last Decade).
• GOLD (parser) is an open source BNF parser.

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2, 1
(mildly basic oxide)
Electronegativity 2.00 (scale Pauling)
Ionization energies 1st: 1007.1 kJ/mol
2nd: 1810 kJ/mol
3rd: 3300 kJ/mol
Atomic radius 150 pm
Atomic radius (calc.
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1
(mildly basic oxide)
Electronegativity 1.62 (scale Pauling)
Ionization energies 1st: 589.4 kJ/mol
2nd: 1971 kJ/mol
3rd: 2878 kJ/mol
Atomic radius 190 pm
Atomic radius (calc.
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2
(Amphoteric oxide)
Electronegativity 2.33 (scale Pauling)
Ionization energies
(more) 1st: 715.6 kJmol⁻¹
2nd: 1450.5 kJmol⁻¹
3rd: 3081.
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3, 5
(mildly acidic oxide)
Electronegativity 2.02 (scale Pauling)
Ionization energies
(more) 1st: 703 kJmol⁻¹
2nd: 1610 kJmol⁻¹
3rd: 2466 kJmol⁻¹
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4, 2
(amphoteric oxide)
Electronegativity 2.0 (scale Pauling)
Ionization energies 1st: 812.1 kJ/mol
Atomic radius 190 pm
Atomic radius (calc.) 135 pm
Miscellaneous
Magnetic ordering nonmagnetic
Electrical resistivity (0 C) (α) 0.
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Astatine (IPA: /ˈastətiːn/) is a chemical element in the periodic table that has the symbol At and atomic number 85.
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Radon (IPA: /ˈreɪdɒn/) is a chemical element that has the symbol Rn and atomic number 86. Radon is a radioactive noble gas that is formed by the decay of radium.
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electron configuration is the arrangement of electrons in an atom, molecule, or other physical structure (e.g., a crystal). Like other elementary particles, the electron is subject to the laws of quantum mechanics, and exhibits both particle-like and wave-like nature.
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The lanthanide (or lanthanoid) series comprises the 15 elements with atomic numbers 57 through 71, from lanthanum to lutetium^[1]. All lanthanides are f-block elements, corresponding to the filling of the 4f electron shell, except for lutetium which is a d-block
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Lanthanum (IPA: /ˈlanθənəm/) is a chemical element in the periodic table that has the symbol La and atomic number 57.
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3, 4
(mildly basic oxide)
Electronegativity 1.12 (scale Pauling)
Ionization energies
(more) 1st: 534.4 kJmol⁻¹
2nd: 1050 kJmol⁻¹
3rd: 1949 kJmol⁻¹
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For other meanings of the abbreviation Pr, see PR.

General
Name, Symbol, Number left=cerium | right=neodymium | above=- | below=Pa | color1=#ffbfff | color2=black }}
Chemical series lanthanides
Group, Period, Block n/a, 6, f
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Neodymium (IPA: /ˌniːə(ʊ)ˈdɪmiəm, ˌniə(ʊ)-/) is a chemical element in the periodic table that has the symbol Nd and atomic number 60.
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Promethium (IPA: /prə(ʊ)ˈmiːθiəm/) is a chemical element in the periodic table that has the symbol Pm and atomic number 61.
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