ELEMENTS AND COMPOUNDS

Science Chapter 3 Grade 6

MODULE OBJECTIVES

• .What is Atom ?• Elements & Compounds• Difference between Element , compound & mixture• Classification of Element• Chemical Pictures• Chemical Symbols• Chemical Symbols -Rules• Molecules and Molecular formula• Valency• Worksheets

WHAT IS ATOM ?

Atoms are the smallest bits of ordinary matter and are made from particles called

1 Protons (which carry a positive electrical charge) 2 Neutrons (which carry no electrical charge) 3 Electrons(which carry a negative electrical charge). The protons and neutrons cluster together in the central part of the

atom, called the nucleus, The electrons 'orbit' the nucleus. A particular atom will have the same number of protons and

electrons . Most atoms have at least as many neutrons as protons.

ELEMENTS & COMPOUNDS

• .

ELEMENTS & COMPOUNDS

An element is a substance that is made entirely from one type of atom. For example, the element hydrogen is made from atoms containing just one proton and one electron, Block A &C

A compound is a substance made from two or more different elements that have been chemically joined. Some examples of compounds are water (H2O) ,table salt (NaCl). Block B

DIFFERENCE BETWEEN ELEMENT , COMPOUND & MIXTURE

Element :Consists of only one kind of atom,Cannot be broken down into a simpler type of matter by either physical or chemical means, andCan exist as either atoms (e.g. argon) or molecules (e.g., nitrogen).Compound :consists of atoms of two or more different elements bound together,can be broken down into a simpler type of matter (elements) by chemical means (but not by physical means),has properties that are different from its component elements, andalways contains the same ratio of its component atoms.

CONTINUE…

Mixture :Consists of two or more different elements and/or compounds physically intermingled,Can be separated into its components by physical means, andOften retains many of the properties of its components.Example :Mercury is a Liquid element . Silver & gold is solid element , people wear silver and gold chain. High flying Balloons which has hydrogen filled in.Water H20 is a Liquid Compound ElementCarbon dioxide is a Gas Compound element.Salt water is a Mixture , can be separated by evaporation.

Note : As hydrogen is highly inflammable, now a days helium is used in balloons instead of hydrogen

ACTIVITY 1 -CLASSIFICATION OF ELEMENT

KNOW THIS Robert Boyle was the first scientist to use teem elemen

Lavoisier , a french chemist, was the first to give definition of an element . he defined an element as basic from of matter that cannot be broken down into simple substances by any chemical

LavoisierRobert Boyle

ACTIVITY - BURNING SUGAR

Take Half a spoon of sugar in the test tube and heat it using spirit lamp. What happens It becomes liquid Continue heating it becomes BrownStill continue heating , you will see black residue. Reheat this residue strongly, does color change ?No, remain as it is, this Black residue is the element Carbon.

https://www.youtube.com/watch?v=o4r4uvuzRZg

CHEMICAL PICTURES

It is difficult to mention the names of elements in all situations. There was a need for international method to identify elements . hence scientists have given symbols to denote them.

Simple Pictures used to denote element was started by Greeks and continued by Johan Dalton.

as more element were discovered difficulty arose to remember them.

CHEMICAL SYMBOLS

A Swedish chemist J .J. berzilius replaced these Pictures by symbols. As his system is good and it is used event today.

While writing the symbols of element we have to follow certain rules :

Rule 1. Generally symbols of element should be represented by first letter of their names.

CHEMICAL SYMBOLS – RULE 2

Difficulty arose then the names of 2 or 3 elements began with the same letter.

Rule 2 if the name of 2 elements begin with the same letter when first 2 letter are taken. the first letter is always written in capital and the second letter should be written small

Carbon and cobalt, both begin with C. then what should be the symbol of cobalt?

Note : There is a lot of difference between Co, the metal cobalt and CO, the deadly gas carbon-monoxide

CHEMICAL SYMBOLS – RULE 3

If the First 2 letter of the elements are the same then next prominent letter should be taken.

Ex : Magnesium and Manganese have the first 2 letters the same. In this case symbol of manganese is Mn and Magnesium is Mg.

CHEMICAL SYMBOLS – RULE 4

Symbols of some elements are derived from their Latin origin. while writing symbols using Latin names the same rules are followed.

MOLECULES

Molecules form when two or more atoms form chemical bonds with each other. It doesn't matter if the atoms are the same or are different from each other. if the atoms of the same kind combine, a molecules of that element is formed.

H2O (water) N2 (nitrogen) O3 (ozone) CaO (calcium oxide) C6H12O6 (glucose, a type of sugar)

Single atoms of elements are not molecules. A single oxygen, O, is not a molecule. When oxygen bonds to itself (e.g., O2, O3) or to another element (e.g., carbon dioxide or CO2), molecules are formed.

MOLECULAR FORMULA

An expression which states the number and type of atom present in a molecule of a substance.

Examples: There are 1 carbon atoms and 2 oxygen atoms CO2

A molecules of water is represented a H2O. here 2 Atoms of hydrogen are attached to 1 atom of oxygen

There are 6 C atoms and 14 H atoms in a hexane molecule , which has molecular formula CH4 .

VALENCY

• The combining power of an atom of an element is referred to as its valency.

Depending upon its valencies an element is called :1. Monovalent (Valency 1)2. Divalent ( Valency 2)3. Trivalent (Valency 3)4. Tetravalent ( Valency 4)

MOLECULAR FORMULA TABLE

USES OF SYMBOLS AND MOLECULAR FORMULAE :

The names of the elements and compounds can be denoted in short forms which save time and place while writing

Formula indicates the names of all the elements present in a compound.

The number of atoms present in the compound can be known easily

the proportion or ratio in which atoms combine can be know.

WORK SHEET

Four Alternatives are given under each complete /incomplete statement. Choose correct answer and put a tick mark against it.1. The liquid filled in thermometer is

a) Oil b) brominec) Mercury c) Spirit

2. The chemical symbol used to represent silver is a) Ag b) AuC) Al d) Ar

3. The Chemical symbol of the element having Latin name is a) Ru b) Npc) Fe d) Ni

WORK SHEET

4. It is an example for compound a) Carbon b) Nitrogen gas c) air d) Carbon dioxide 5.The Molecular formula of carbon dioxide is a) CO b) CO2

c) CO3 d) C2O6 . Potassium permanganate has one atom of potassium , one atom of manganese and four atoms of oxygen : a) KMno b) KMn4o c) K4Mno d) KMnO4

WORK SHEET

7. Ammonia (NH3) had 3 atom of hydrogen and one atom Nitrogen . What is the valency of nitrogen? a) 1 b)2

c)3 d)48. One atom of magnesium combines with two chlorine atoms to form Magnesium chloride.

a) Mg2 Cl b) MnCl2 c) MgCl2 d) Mn2Cl

9.In Methane One atom of carbon combines with four atoms of a) Hydrogen b) oxygen c) Nitrogen d) Carbon

WORK SHEET

Fill in the Blanks with suitable words :1. Each substance is Made up of . 2. The Greek Used to represent Element.3.The Method of representing elements by symbols was introduce by __________ .4.The Latin name of sodium is __________.5. The elements present in nitric acid are Nitrogen, Hydrogen and _____.6. The Molecular formula of hydrogen molecule is____.

7. The Smallest particle that has all the properties of an element is called _______ .8. Complete the following :a.________ + Oxygen ——> Magnesium oxideb. Hydrogen + __________ ———> Water

elements

picture

Berzelius

Natrium

Oxygen

H2

Molecule

Magnesium

Oxygen

WORK SHEET

Match The compounds given in list A with the molecular formulae given in list ‘B”

1. Ammonia a) NaCl 2.Sodium chloride b)CO2

3.Sulphuric acid c) Au 4.Water d)NH3

5.Carbon dioxide e) H2O 6.Gold f) H2so4

WORK SHEET

Match the Latin names of the following elements :1. Potassium Aurum2.Sodium Plumbum3.Iron Ferrnum4.Tin Stibium6.Gold Natrium7.Lead Argentum8.Antimony Kalium9.Silver Stannum

WORK SHEET

Match the chemical names of the following compound :Column no. 1 Column no. 21. NaOH - Copper Sulphate2.AlCl3 - Magnesium Sulphate 3.Na2CO3 - Nitric Acid4.CuSO4 - Aluminium Chlorite6.MgCl2 - Magnesium Chloride7.HNO3 - Barium Chloride8.BaCl2 - Sodium Carbonate9.MgSO4 - Sodium Hydroxide