CHEMISTRY

ELEMENTSA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is 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.[1

ATOMSThe atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen1 which is the only stable nuclide with no neutron).

Non-metal, or non-metal, is a term used in chemistry when classifying the chemical elements. On the basis of their general physical and chemical properties, every element in the periodic table can be termed either a metal or a non-metal. (A few elements with intermediate properties are referred to as metalloids.)

Metals and Non-metals.

1 1H

2He

2 3Li

4Be

5B

6C

7N

8O

9F

10Ne

3 11Na

12Mg

13Al

14Si

15P

16S

17Cl

18Ar

4 19K

20Ca

21Sc

22Ti

23V

24Cr

25Mn

26Fe

27Co

28Ni

29Cu

30Zn

31Ga

32Ge

33As

34Se

35Br

36Kr

5 37Rb

38Sr

39Y

40Zr

41Nb

42Mo

43Tc

44Ru

45Rh

46Pd

47Ag

48Cd

49In

50Sn

51Sb

52Te

53I

54Xe

6 55Cs

56Ba

* 72Hf

73Ta

74W

75Re

76Os

77Ir

78Pt

79Au

80Hg

81Tl

82Pb

83Bi

84Po

85At

86Rn

7 87Fr

88Ra

** 104Rf

105Db

106Sg

107Bh

108Hs

109Mt

110Ds

111Rg

112Uub

113Uut

114Uuq

115Uup

116Uuh

117Uus

118Uuo

8 119Uue

120Ubn

* Lanthanoids 57La

58Ce

59Pr

60Nd

61Pm

62Sm

63Eu

64Gd

65Tb

66Dy

67Ho

68Er

69Tm

70Yb

71Lu

** Actinoids 89Ac

90Th

91Pa

92U

93Np

94Pu

95Am

96Cm

97Bk

98Cf

99Es

100Fm

101Md

102No

103Lr

Compounds • A chemical compound is a pure chemical substance consisting of two or more

different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms[3] that are held together in a defined spatial arrangement by chemical bonds. Chemical compounds can be compound molecules held together by covalent bonds, salts held together by ionic bonds, metallic compounds held together by metallic bonds, or complexes held together by coordinate covalent bonds. Substances such as pure chemical elements and elemental molecules consisting of multiple atoms of a single element (such as H2, S8, etc.) are not considered chemical compounds.[5]

Chemical reactions • A chemical reaction is a process that leads to the transformation of one

set of chemical substances to another.[1]. They are studied by chemists under a field of science called chemistry. It can be either spontaneous that is requiring no input of energy or non-spontaneous, that often comes about only after input of some form of energy, viz. heat, light or electricity.

Reaction rate • The reaction rate or rate of reaction for a reactant or product in a particular

reaction is intuitively defined as how fast a reaction takes place. For example, the oxidation of iron under the atmosphere is a slow reaction which can take many years, but the combustion of butane in a fire is a reaction that takes place in fractions of a second.

• Chemical kinetics is the part of physical chemistry that studies reaction rates. The concepts of chemical kinetics are applied in many disciplines, such as chemical engineering, enzymologist and environmental engineering.

Chemical reactions • A chemical reaction is a process that leads to the transformation of one set of

chemical substances to another.[1]. They are studied by chemists under a field of science called chemistry. It can be either spontaneous that is requiring no input of energy or non-spontaneous, that often comes about only after input of some form of energy.

A chemical reactions

Chemical changes• Chemical Changes Chemical changes take place on the molecular level. A chemical change

produces a new substance. Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan, and mixing hydrochloric acid and sodium hydroxide to make salt and water.

Physical changes

Physical changes are concerned with energy and states of matter. A physical change does not produce a new substance. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle.