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Chemical Combination
The number of known elements till now is 118
Those elements are classified according to their properties and electronic
. structure into metals , non-metals and noble gases .
Metals : They are the elements which have less than 4 electrons in - 1
. the outermost energy level
: The properties of metals
.Solids except Mercury (Hg) which is liquid- 1 Have metallic luster- 2 Good conductor of heat and electricity- 3 Malleable and ductile- 4 .Containing 1,2 or 3 electrons in the outer electron shells- 5 During the chemical reaction , atoms of metals give (lose) their outermost electrons to other atoms (to complete the outermost energy level with electrons) and become positive ions (which carry a number of positive charges equal to the number of the given electrons) Positive ion: It is the atom which loses an electron or more during the
. chemical reaction
: Examples of metal atoms
Sodium ( Na)- 1
Elements
Metals Non-metals Noble gases
Magnesium ( Mg)- 2 Aluminum ( Al)- 3 G.R. When the atom loses an electron or more during the chemical
. reaction , it changes to a positive ion Bec. The number of positive protons becomes more then the number of . negative electrons
Non-metals : They are the elements which have more than 4- 2
. electrons in the outermost energy level
: Properties of nonmetals
.Solids and gases except Bromine (Br) which is liquid- 1 Have no luster- 2 Bad conductor of heat and electricity except Graphite (Carbon) which- 3
. is a good conductor of electricity .Not malleable or ductile- 4 .Containing 5, 6 or 7 electrons in the outer shells- 5 During the chemical reaction , atoms of non metals gain electrons from other atoms and become negative ions which carry a number of negative . charges equal to the number of the gained electrons
Negative ion: It is the atom which gains an electron or more during the
. chemical reaction
So they are monoatomic ( consists of one atom) and don’t form positive
. or negative ions ? G.R. Noble gases don’t participate in the chemical reaction . Bec. The outer most energy level is completely filled with electrons : Examples of noble gases Electronic configuration No. of neutrons No. of protons No. of electrons The atom of the inert gas He 2 2 2 Ne Ar Exercise Electronic configuration of the ion Its electronic Its type Type of ion configuration Element N 7 Na 11 Al 13 O 16 Cl 17 Ar 18 Points of comparison The atom The ion Charged [positive or negative] ion Electrically Neutral More or less than the no. of protons Equal the no. of protons The number of electrons
Note; Helium 2 He is a noble gas
Chemical bonds
Atoms combine with each other forming molecules through " "Chemical bonds There are 2 types of bonds which are Ionic bond 2-Covalent- 1 bond Ionic bond: It is a bond resulting from the electric attraction- 1
. between a positive ion and a negative ion ? How is ionic bond is formed Ionic bond is formed between a metal and a nonmetal where metal atom loses electron and changes into a positive ion and nonmetal atom gains the electron lost from metal atom and changes into a negative ion then a strong electrical attraction between positive and negative ions occurs through the ionic bond : Examples :Formation of sodium chloride (table salt) molecule (NaCl)- 1 :Formation of magnesium oxide molecule (MgO)- 2 G.R. Ionic bond produces compounds molecules only and not . produce elements molecules . Bec. Ionic bond is formed bet. A Metal and a Non-metal G.R. It is impossible to combine sodium and magnesium ? together to form a compound . Bec. Each of them loses the outer most electrons Covalent bond: It is a bond occurs between the atoms of - 2 nonmetals through (sharing) participation with electrons to . complete the outer energy level of each atom
.It is represented by 3 lines ( Ξ ) joining the two atoms- Ex: Nitrogen molecule (N 2 ) G.R. The covalent bond can produce elements and ? compounds Bec. It can be formed bet. Two similar non-metals to form element
. or bet. Two different non-metals to form compound Note: Covalent bond is formed by sharing with electrons Covalent bond produce element molecules between 2 similar nonmetals Covalent bond produce compound molecules between 2 different nonmetals Ionic bond Covalent bond It is formed by sharing of one- 1 . pair of electrons or more It is formed between two- 2 . nonmetal elements It is formed due to sharing of- 3 . electrons between the atoms It has 3 types (single ,double- 4 and triple) It produces element and- 5 . compound molecules It is formed by losing or- 1 gaining of electrons It is formed between metal - 2 and nonmetal elements It is formed due to the- 3 electrical attraction between the . positive and negative ions .It has one type- 4 It produces compound- 5 . molecules only Positive ion Negative ion It is the atom which gains an electron or more during the . chemical reaction It is the atom which loses an electron or more during the . chemical reaction Carry positive charges Carry negative charges The number of electrons is more than the number of protons The number of electrons is less than the number of protons
