LESSON 4: PARTICULATE NATURE OF MATTER

LESSON 4: PARTICULATE NATURE OF MATTER

Behavioural objectives: at the end of this lesson, you should be able to:

1.      Write the electronic configuration of the first 20 elements correctly, using S,P,D,F format 

2.      State the Dalton’s atomic theory and its modification

3.      Solve problems related to isotope and relative atomic mass

4.      Differentiate between, molecule, ions and atom.

5.      Define isotopes and give examples of element that exhibit isotopy. 

CONTENT

What is a matter? Matter is defined as anything that has mass and occupies space. However, matter consists of some particles which could be atom, molecules, or ions   

Atoms: This is the smallest indivisible particle of an element which can take part in a chemical reaction. 

Molecules; This is the smallest part of a substance which can have a separate existence and still possess the properties of the substance. E.g. the tiny pieces of slice bread, a drop of water, hair strand e.t.c

Ion: An ion is any atom or group of atom which possesses an electric charge. There are 2 types of ions which are

1.       Cat ion: this is a positive charged ion. e.g. Na⁺ , Ca²⁺ , Fe³⁺  and

2.       An ion: this is a negative charged ion.  e.g  Cl^{- ­} , No ₃^- _, OH ^-  e.t.c

    There are natural phenomenon which can be used to support the statement that matter is made up of particles. These include

1.      Diffusion: it is the movement of molecules of a substance from a region of higher concentration to the region of lower concentration, until it is evenly distributed. E.g. movement of scent of perfumes, aroma of soup e.t.c

2.      Evaporation: it is the process whereby molecules of a liquid of  highest kinetic energy escape into the atmosphere through the surface of the liquid. e.g. evaporation of water.

3.      Osmosis: this is the movement of solvent molecule from the region of lower concentration to a region of higher concentration through a semi permeable membrane. E.g. movement of water molecule from the soil to the root of plant.

4.      Brownian motion

5.      Sublimation

                              

DALTONS ATOMIC THEORY AND ITS MODIFICATIONS

S/N	Dalton’s atomic theory	Modification
1	Matter is made up of small indivisible particle called atoms.	Matter is made up of small particles, which might be proton, neutron or electron.
2	Atom can neither be created nor destroyed.	Atom can be created and can be destroyed. During chemical reactions there is change in heat content of the atoms. Also radioactivity prove it.
3	The atoms of the same element are alike in every aspect and differ from atoms of all other elements.	Isotopes prove it wrong as atoms of the same element can have different masses. Chlorine has two isotopes which are different in atomic mass but have the same atomic number.
4	Chemical compound were made by the union of small whole number of atoms.	Polymers [organic compounds] are made from large number of atoms joined together.

                          

ATOMIC STRUCTURE

Atoms are found to contain three types of particles which are protons, neutrons and electrons. It consists of centrally placed nucleus which is surrounded by a cloud of electrons.

            The nucleus contains proton and neutrons with mass of one each. Proton is positively charged, neutron is neutrally charged while electron is negatively charged.

The electron revolves round the nucleus in an orbital in order to neutralize the positive charge in the nucleus. The atom is electrically neutral because the number of electrons revolving round the nucleus is equals to the number of protons in the nucleus.

The table below indicates the properties of sub-atomic particles.

Particles Proton Neutron Electron

Mass 1 1 1/1840

Charge +1 No charge -1

ELECTRONIC CONFIGURATION

            This refers to the way electrons are arranged outside and around the nucleus. The electrons are arranged in orbits known as shells.

            There are seven shells in all which are K,L,M,N,O,P&Q. These shells are sub-divided into orbitals called S,P,D,F orbitals.

ORBITAL TYPES IN A SHELL

Shell K L M N

Shell number 1 2 3 4

Orbital type 1s 2s, 2p 3s, 3p, 3d 4s,4p,4d,4f

Maximum electron 2 8 18 32

From the table above, we can see that K –shell have just one orbital which is S – orbital, and S – orbital can only take maximum electrons of two. Therefore K – shell can have 2 electrons, and for L shell, it has two orbital which are 2s and 2p respectively. P – orbital can take 6 electrons, if we add 6 to 2 it makes 8 electrons. Likewise for D- orbital and F – orbital which can take 10 and 14 electrons respectively.      

The sequence of filling up the orbitals with electrons is as follows:

1s, 2s 2p, 3s 3p, 4s 3d,  note: that 4s is filled before 3d because 4s energy level is lower than 3d energy level. Now let’s take a look at the electronic configuration of the first 20 elements.

Elements	Atomic number	Symbol	Configuration
Hydrogen	1	H	1s1
Helium	2	He	1s2
Lithium	3	Li	1s2,2s1
Beryllium	4	Be	1s2,2s2
Boron	5	B	1s2,2s2 2p1
Carbon	6	C	1s2,2s2 2p2
Nitrogen	7	N	1s2, 2s2 2p3
Oxygen	8	O	1s2, 2s2 2p4
Fluorine	9	F	1s2, 2s2 2p5
Neon	10	Ne	1s2, 2s2 2p6
Sodium	11	Na	1s2, 2s2 2p6, 3s1
Magnesium	12	Mg	1s2, 2s2 2p6, 3s2
Aluminium	13	Al	1s2, 2s2 2p6, 3s3
Silicon	14	Si	1s2, 2s2 2p6, 3s2 3p2
Phosphorus	15	P	1s2,2s2 2p6, 3s2 3p3
Sulphur	16	S	1s2,2s2 2p6, 3s2 3p4
Chlorine	17	Cl	1s2, 2s2 2p6, 3s2 3p5
Argon	18	Ar	1s2,2s2 2p6, 3s2 3p6
Potassium	19	K	1s2,2s2 2p6, 3s2 3p6, 4s1
Calcium	20	Ca	1s2,2s2 2p6, 3s2 3p6, 4s2