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 elements The atom is electrically neutral in ordinary state because no. of positive protons are equal to the no. of negative electrons

Classification of elements Elements 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 gases Atom of inert gas No. of electrons No. of protons No. of neutrons Electron configuratio n P 2n 10p 10n 18P 22n 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

Comparisons Points of comparison Atom Ion Electrically: NeutralCharged (-) or (+) No. of electrons:Equal to the no. of protons More or less than no. of protons

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

Nitrogen atom (N)

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)

Comparison Positive 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 bond 2- 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 (+) ion 2- Non-metal atom gains electron(s) lost from metal atom & changes into (-) ion 3- A strong electrical (electrostatic) attraction between (+) & (-) ions occur through ionic bond

Examples of ionic bonds 1- Formation of table salt

2-Formation of Magnesium oxide First 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 atom Steps of formation of covalent bonds: 1- Two non-metal atoms interact together, no one loses or gains any electrons 2- Each atom shares the other with a no. of electrons equal to the no. needed to complete its outer shell 3- 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 electronsFormed 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 typeThree types : single, double, triple Produces compound molecules onlyProduces 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 configuration K L M N Molecule Type of bond NaCl Ionic bond Triple covalent Question (2) (A):

Model answers of lesson 1 Question (2) (B):

Model answers of lesson 1 Question (3) (A): Element Electron configuration K L M N Its type Its ion Non-metal metal 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