Matter & Energy


Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.

Alphabetic list of Chemical Elements (N-O-P)

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Name: Neodymium
Symbol: Nd
Atomic Number: 60
Atomic Weight: 144.24
Group: Lanthanide
Date Discovered: series 1885
Discovered By: Carl von Welsbach

Name: Neon
Symbol: Ne
Atomic Number: 10
Atomic Weight: 20.1798
Group: Noble gases
Date Discovered: 1898
Discovered By: William Ramsay and Morris Travers

Name: Neptunium
Symbol: Np
Atomic Number: 93
Atomic Weight: (237)
Group: Actinide
Date Discovered: series 1940
Discovered By: Edwin McMillan and Philip Abelson

Name: Nickel
Symbol: Ni
Atomic Number: 28
Atomic Weight: 58.6934
Group: Transition metals
Date Discovered: 1751
Discovered By: Axel Cronstedt

Name: Niobium
Symbol: Nb
Atomic Number: 41
Atomic Weight: 92.9064
Group: Transition metals
Date Discovered: 1801
Discovered By: Charles Hatchett

Name: Nitrogen
Symbol: N
Atomic Number: 7
Atomic Weight: 14.0067
Group: Nonmetals
Date Discovered: 1772
Discovered By: Daniel Rutherford

Name: Nobelium
Symbol: No
Atomic Number: 102
Atomic Weight: (259)
Group: Actinide
Date Discovered: series 1958
Discovered By: Albert Ghiorso, Torbjørn Sikkeland, J. R. Walton, and Glenn Seaborg

Name: Osmium
Symbol: Os
Atomic Number: 76
Atomic Weight: 190.23
Group: Transition metals
Date Discovered: 1804
Discovered By: Smithson Tennant

Name: Oxygen
Symbol: O
Atomic Number: 8
Atomic Weight: 15.9994
Group: Nonmetals
Date Discovered: 1774
Discovered By: Joseph Priestley and Karl Scheele, independently of each other

Name: Palladium
Symbol: Pd
Atomic Number: 46
Atomic Weight: 106.42
Group: Transition metals
Date Discovered: 1804
Discovered By: William Wollaston

Name: Phosphorus
Symbol: P
Atomic Number: 15
Atomic Weight: 30.9738
Group: Nonmetals
Date Discovered: 1674
Discovered By: Hennig Brand

Name: Platinum
Symbol: Pt
Atomic Number: 78
Atomic Weight: 195.08
Group: Transition metals
Date Discovered: 1557
Discovered By: Julius Scaliger

Name: Plutonium
Symbol: Pu
Atomic Number: 94
Atomic Weight: (244)
Group: Actinide
Date Discovered: series 1940
Discovered By: Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl

Name: Polonium
Symbol: Po
Atomic Number: 84
Atomic Weight: (209)
Group: Other metals
Date Discovered: 1898
Discovered By: Marie and Pierre Curie

Name: Potassium
Symbol: K
Atomic Number: 19
Atomic Weight: 39.0983
Group: Alkali metals
Date Discovered: 1807
Discovered By: Humphry Davy

Name: Praseodymium
Symbol: Pr
Atomic Number: 59
Atomic Weight: 140.908
Group: Lanthanide
Date Discovered: series 1885
Discovered By: Carl von Welsbach

Name: Promethium
Symbol: Pm
Atomic Number: 61
Atomic Weight: (145)
Group: Lanthanide
Date Discovered: series 1945
Discovered By: J. A. Marinsky, Lawrence

Name: Protactinium
Symbol: Pa
Atomic Number: 91
Atomic Weight: 231.036
Group: Actinide
Date Discovered: series 1913
Discovered By: Kasimir Fajans and O. Göhring