chemical combination unit -1 lesson -1 made by dr. niveen fawzy
TRANSCRIPT
Chemical Combination Unit -1
Lesson -1
Made By Dr. Niveen Fawzy
The atom & the ion
Element• Is composed of
Molecules• Each
molecule consists of
Atoms
The no. of well known elements are 116 elementsThe atom is electrically neutral in ordinary state because no. of positive protons are equal to the no. of negative electrons
Classification of elementsElements are classified according to their
properties & electronic structure into:
1-Metals
2-Non-metals
3-Noble gases
First : Noble (inert) Gases
• They are elements in which the outermost electron shells are completely filled with electrons , so they don’t participate in any chemical combination in ordinary conditions
• They are monoatomic • They don’t form positive or negative ions in ordinary
conditions
Examples of noble gasesAtom of inert gas
No. of electrons
No. of protons
No. of neutrons
Electron configuration
2 2 2
10 10 10
18 18 22
2P2n
10p10n
18P22n
K
2
K L
2 8
K L M
2 8 8
Nobel gases
Second: Metals & non-metals
Physical properties of both
Chemical properties of both Metals Non-metals
They are elements which have less than (4) electrons in the outermost energy level
They are elements which have more than (4) electrons in the outermost energy level
During chemical reactions metals lose (give) their outermost electrons to other atoms & change to (+) ion
During chemical reactions non-metals gain electrons from other atoms to complete the outermost energy level & change to (-) ion
Mercury is the only liquid metal, while Bromine is the only liquid non-metal
ComparisonsPoints of comparison
Atom Ion
Electrically: Neutral Charged (-) or (+)
No. of electrons: Equal to the no. of protons
More or less than no. of protons
Examples of metals
Examples of metals
Examples of metals
Give reason:• When the atom loses an electron or more during chemical
reaction, it changes into positive ion • Because the no. of electrons becomes less than the no. of
protons• What is an ion?• Its an atom which loses or gains an electron or more during
chemical reactions• What is a positive ion?• Its an atom that loses one or more electrons during the
chemical reaction & carries a no. of positive charges equal to the no. of given electrons
Examples of non-metals
Examples of non-metals
Examples of non-metals
Nitrogen atom (N)
Nitrogen ion (
Give reason:• When the atom gains an electron or more during
chemical reactions , it changes into a negative ion• Because the no. of electrons becomes more than the no.
of protons • What is a negative ion?• It’s the atom which gains an electron or more during the
chemical reaction & carries a no. of negative charges equal to the no. of gained electrons
• N.B Hydrogen is a gaseous non-metal element although it has only one electron in the outermost level (K)
ComparisonPositive ion (cation) Negative ion (anion)
A metal atom that loses an electron or more during chemical reaction
A non-metal atom that gains an electron or more during chemical reaction
It carries positive charges equal to the no. of lost electrons
It carries negative charges equal to the no. of gained electrons
No. of electrons is less than no. of protons
No. of electrons is more than no. of protons
No. of its energy levels is less than that of its atom
No. of its energy levels is equal to that of its atom
Try to think:• What happens to the atomic diameter of an atom when
it loses or gains an electron or more?• When an atom loses an electron or more its diameter &
volume decrease due to lackness of electrons, & attraction of nucleus to remaining electrons increase , so a positive ion diameter is smaller than its atomic diameter
• When an atom gains an electron or more its diameter & volume increase due to increase in the no. of electrons ,& repelling increase between electrons , a negative ion diameter is bigger than its atomic diameter
Chemical bonds
• Atoms combine together to form molecules through chemical bonds
• We will study 2 types of bonds:1- Ionic bond2- Covalent bond
First: Ionic bond• It’s a type of chemical bond that occurs between a metal
atom & a non-metal atom resulting from electric attraction between a (+) &(-) ion
• Steps of formation of ionic bond:1- Metal atom loses electron(s) & changes into a (+) ion2- Non-metal atom gains electron(s) lost from metal atom & changes into (-) ion3- A strong electrical (electrostatic) attraction between (+) & (-) ions occur through ionic bond
Examples of ionic bonds1- Formation of table salt
2-Formation of Magnesium oxideFirst step :
Second step:
Third step:
Its a bond occurred among atoms of non-metals through the participation of each atom with the same no. of electrons to complete the outer electron shell of each atomSteps of formation of covalent bonds:1- Two non-metal atoms interact together , no one loses or gains any electrons2- Each atom shares the other with a no. of electrons equal to the no. needed to complete its outer shell3- An interference occurred among both atoms resulting in covalent bond
Second : Covalent bond
Types of covalent bond• There are 3 types of covalent bonds:• 1- Single covalent bond• 2- Double covalent bond • 3- Triple covalent bond First: Single covalent bond• Its bond arises between 2 non-metals sharing each other
with one electron• Represented by one line joining the two atoms { }
Examples of single covalent bond• 1-Hydrogen molecule
Each hydrogen atom shares with one electron to complete (K) level & become more stable
Single covalent bond 2- Water molecule •
The oxygen atom shares each hydrogen atom with one electron , to complete the outermost shell of all 3 atoms
Single covalent bond• 3- Hydrogen chloride molecule:• The hydrogen & chlorine atoms each share each other
with one electron
Double covalent bond Oxygen molecule
Each oxygen atom shares the other with 2 electrons to complete the outermost shell (L) with 8 electrons & become more stable
The double covalent bond arises between 2 non-metal atoms sharing each other with 2 electrons & is represented by (=) joining 2 atoms
Triple covalent bond Triple covalent bond arises between 2 non-metal atoms sharing each other with 3 electrons to complete the outermost shell & become more stable & is represented by 3 lines Nitrogen molecule
Comparison Ionic bond Covalent bond
Formed by losing or gaining of electrons Formed by sharing one pair of electrons or more
Arises between metal & non-metal elements
Arises between 2 non-metal elements
Formed between 2 atoms of 2 different elements
May be formed between 2 elements of same element
Formed due to electrical attraction between (+) &(-) ions
Formed due to sharing of electrons between atoms
Its only one type Three types : single , double , triple
Produces compound molecules only Produces element & compound molecules
Enrichment information• The Egyptian scientist Ahmed Zweil has been granted
Nobel prize in chemistry in 1999 due to inventing new brands of camera working via laser technologies
Model answers of book lesson 1-unit1• Question (1) (A):• 1- Metal atom 2- Ionic bond 3-Non-metal atom• 4- Triple covalent bond 5- Noble (inert) element• 6- Metals 7- Non-metals• Question (1) (B):• Because iron is a metal element which is malleable so it
will not break, while coal is a non-metal which is not malleable , breaks easily
Model answers of book lesson 1
Atom Electron configurationK L M N
Molecule Type of bond
2 8 1 -
2 8 7 -
NaCl Ionic bond
2 5 - - Triple covalent
Question (2) (A):
Model answers of lesson 1• Question (2) (B):
Model answers of lesson 1• Question (3) (A):
Element Electron configurationK L M N
Its type Its ion
2 8 6 - Non-metal
2 8 2 - metal
2 8 8 - inert gas no ion
Model answers of lesson 1• Question (b) Give reason:• 1- Because sodium (metal) atom joins with chlorine (non-
metal) atom by transferring one electron from Na to Cl & ionic compound is formed . While chlorine atom joins with other chlorine atom by sharing with one electron for each atom to form covalent molecule.
• 2- Because the no. of electrons becomes less than no. of protons
• 3- Because the no. of electrons becomes more than the no. of protons
Model answers of lesson 1• 4- Because ionic bond arises between 2 different atoms
(metal & non-metal) , while covalent bond arises between 2 similar or different non-metal atoms
• 5- Because each oxygen atom shares with 2 electrons to form double covalent bond
• 6- Because magnesium loses 2 electrons & change into (+) ion , while oxygen gains the 2 electrons lost by (Mg) & changes into (-) ion , then electric attraction occurs between both ions
Model answers of lesson 1• Question (4): comparison:• Refer to previous slides for comparison tables• Question (5):• What is a positive ion?• Its an atom that loses one or more electrons during the chemical reaction
& carries a no. of positive charges equal to the no. of given electrons• What is a negative ion?• It’s the atom which gains an electron or more during the chemical reaction
& carries a no. of negative charges equal to the no. of gained electrons• What is an ion?• Its an atom which loses or gains an electron or more during chemical
reactions