element and compounds

8/8/2019 Element and Compounds

1/14

Chemistry projectOn

Elements & compounds

DONE BY,HABIBA TASKEEN

VI A


2/14

Elements and Compounds are pure substances.

An element is a pure substance that cannot be

decomposed into simpler substances.

Elements are listed in the Periodic Table of the Elements. Each element has a 1 or 2 letter symbol.

A compound is a pure substance that can be decomposed

into simpler substances.

Compounds are made up of two or more elements.

Element- An element is a substance composed of the same type of

atoms (e.g. gold Au, oxygen O2). An element is a pure substance

that cannot be decomposed (broken down) into simpler

substances.

Compound - A compound is a substance made of more than one type

of atom (e.g. water H2O, carbon dioxide CO2).

Molecule - A molecule is the smallest particle of either an element

or a compound.

ELEMENTS
http://www.ausetute.com.au/puresubs.htmlhttp://www.ausetute.com.au/pertable.htmlhttp://www.ausetute.com.au/puresubs.htmlhttp://www.ausetute.com.au/pertable.html


3/14

Elements are the simplest pure substance.

An element can not be changed into a simpler substance

by heating or any chemical process.

The smallest particle of an element that has theproperties of that element is called an atom. An atom is

the basic building block of matter.

All elements are made of atoms.

Atoms of the same element are alike.

Atoms of different elements are different.

There are more than one hundred known elements in the

universe listed on the periodic table of elements.

These elements combine in such a way to create millions

of compounds.

Each element has been given a 1 or 2 letter symbol:

the first letter of the symbol is always a capital letter

eg., H for hydrogen, C for carbon, N for nitrogen

if there is a second letter in the symbol it is a lower case

letter

eg, He for helium, Ca for calcium, Ne for neon

Elements can be present in nature as solids, liquids or

gases.

Elements can be further divided into

metals and non-metals.


4/14

Metals

They are generally solids with characteristics such as

hardness, malleability, ductility high tensile strength, lustre

and ability to conduct heat and electricity.

For example: Copper, iron, zinc etc.

Non-metals

They are generally non-lustrous, brittle, poor conductors of

heat and electricity.

For example: Sulphur, phosphorus, nitrogen etc.

Metalloids

These elements have characteristics common to metals and

non-metals.

For example: Arsenic, tin, bismuth etc.

The atmosphere is mostly made up of the elements

nitrogen (~78%) and oxygen (~21%).


5/14

COMMON ELEMENTS AND SYMBOLS

Element Symbol Element Name Element Symbol Element Name

H Hydrogen Mn Manganese

He Helium Fe Iron

Li Lithium Co Cobalt

C Carbon Ni Nickel

N Nitrogen Cu Copper

O Oxygen Zn Zinc

F Fluorine Br Bromine

Ne Neon Ag Silver

Na Sodium Sn Tin

Mg Magnesium I Iodine

Al Aluminium Ba Barium

Si Silicon W Tungsten

P Phosphorus Pt Platinum

S Sulphur / Sulfur Au Gold

Cl Chlorine Hg Mercury

Ar Argon Pb Lead

K Potassium Cr Chromium

Ca Calcium Ti Titanium

Pu Plutonium U Uranium

Compound


6/14

It is a pure substance that can be decomposed into simpler

substances by some suitable chemical technique. A compound is

formed by combination of two or more elements in a definite

proportion.

For example, water is a compound of hydrogen and oxygenelements present in the ratio of 1: 8.

Properties of compounds

A compound cannot be separated into its constituents by

mechanical or physical means.

For example, if we bring a magnet near a sample of iron

sulphide, the iron present in the iron sulphide cannot beseparated.

Properties of a compound differ entirely from those of its

constituent elements.

For example, water is made up of hydrogen and oxygen.

However, the properties of hydrogen and oxygen (both gases)

are different from water (liquid). Hydrogen is combustible,

oxygen is a supporter of combustion whereas water (made up

of both hydrogen and oxygen) puts out a flame.

Energy changes are involved in the formation of a compound.

For example, iron and sulphur reacts only when heat is

supplied.

The constituent elements in a compound are in a fixed

proportion by weight. In water, hydrogen and oxygen are

present in a fixed ratio of 1:8 by weight.

A compound is a homogenous substance. That is it is same

throughout in properties and composition.

A compound has a fixed melting point and boiling point. For

example, ice melts at 0oC.

NAMING COMPOUNDS


7/14

PREFIX OR

SUFFIX

MEANING EXAMPLE

Mono- There is 1 atom of that type in that

molecule

Carbon monoxide (CO)

Di- There are 2 atoms of that type in the

molecule

Carbon dioxide (CO2)

Bi- Hydrogen is present in the molecule Sodium bicarbonate

(NaHCO3)

-ide There are only 2 types of atoms present

in the molecule

Lead oxide

(PbO)

-ate There are 3 or more types of atoms in

the molecule, and 1 type is oxygen

Calcium carbonate

(CaCO3)

VALENCY TABLE


8/14

Valency - the charge of an ion or radical which has either

lost or gained electrons

Note that metals lose electrons easily to become positive

ions. This is why most metals are good conductors of

electricity.

1+ 2+ 3+ 1- 2- 3-

H 1+ Mg 2+ Al 3+ F 1- O 2-

oxide

PO4 3-

phosphate

Na 1+ Ca 2+ Fe 3+

Ferric

Cl 1- S 2-

sulphide

Li 1+ Cu 2+ Br1- CO32-

carbonate

K1+ Zn 2+ OH 1-

hydroxide

SO42-

sulphate

Ag 1+ Pb 2+ NO31-

nitrate

NH41+

ammonium

Fe 2+

Ferrous

HCO31-

bicarbonate


9/14

WORKING OUT FORMULAE OF IONIC

COMPOUNDS

(THE CROSS-OVER METHOD)

Step 1 - In the ionic compounds to be learnt in junior science,

there are two parts to the ionic compound - the first is a

positive ion (usually a metal e.g. Na1+) and the second is a

negative ion (e.g. Cl1-).

Step 2 - Using the valency table, write the two ions and their

valencies.

Step 3 - Now ignore the positive and negative signs. Cross-

over the top valency number to the bottom of the other ion

symbol. Do this for both.

Step 4 - Write the completed formulae with those samenumbers at the bottom.

Step 5 - If the numbers on each part are the same (e.g. Na1Cl1 or Mg2 O2), ignore them and rewrite the formulae without

them (e.g. Na Cl or Mg O).

Step 6 - Brackets may be used around radicals (groups of

atoms that are charged e.g CO3).


10/14

EXAMPLES

OF

CHEMICAL

NAMES OF

COMPOUNDS

CHEMICAL

FORMULA

CHEMICAL NAME

CO2 carbon dioxide

CO carbon monoxide

Na Cl sodium chloride

Cu O copper oxide

Ag Br silver bromide

K I potassium iodide

H Cl hydrogen chloride (hydrochloric acid)

NH4 Cl ammonium chloride

K OH potassium hydroxide

Na OH sodium hydroxide

Ca (OH)2 calcium hydroxide

Ca S calcium sulphide

Na NO3 sodium nitrate

H NO3 hydrogen nitrate (nitric acid)

Na HCO3 sodium bicarbonate

Zn SO4 zinc sulphate

Mg CO3 magnesium carbonate

Ca SO4 calcium sulphate

Cu CO3 copper carbonate

Al PO4 Aluminium phosphate

Fe SO4 iron sulphate

Fe CO3 iron carbonate

NH4 NO3 Ammonium nitrate

NH4 HCO3 Ammonium bicarbonate

H2 SO4 hydrogen sulphate (sulphuric acid)

Na2 SO4 sodium sulphate

(NH4)2 CO3 Ammonium carbonate


11/14


12/14

EXAMPLES OF NUMBERS AND TYPES OF ATOMS IN

VARIOUS ELEMENTS AND COMPOUNDS

NAME OF

SUBSTANCE

CHEMICAL

FORMULA

ELEMENT OR

COMPOUND

NUMBER AND TYPE

OF ATOMS IN MOLECULE

Hydrogen H2 Element 2 hydrogen atoms

Carbon dioxide CO2 Compound 1 carbon atom

2 oxygen atoms

Water H2O Compound 2 hydrogen atoms

1 oxygen atom

Methane CH4 Compound 1 carbon atom4 hydrogen atoms

Sodium hydroxide NaOH Compound 1 sodium atom

1oxygen atom

1 hydrogen atom

Calcium hydroxide Ca(OH)2 Compound 1 calcium atom

2 oxygen atoms

2 hydrogen atoms


13/14

COMPARISON BETWEEN COMPOUNDS AND

ELEMENTS

Compound Element

Meaning.

A compound is a

substance composed of

two or more different

chemical elements.

An element is a pure

chemical substance

made of same type of

atom.

Ability to Disintegrate A compound can be

separated into simpler

substances by chemical

reactions.

Elements cannot be

broken down into

simpler substances.

Distinguishing Feature. Compounds contain

different elements in a

fixed ratio arranged in a

defined manner through

chemical bonds.

Elements are

distinguished by their

atomic number (number

of protons in their

nucleus).

Representation A compound is An element is


14/14

represented using a

formula.

represented using

symbols.

Types. The list of compounds is

endless but can broadly

be classified as ionic and

covalent.

There are about 117

elements that have been

observed.

Examples Sodium chloride (NaCl),

Sodium bicarbonate

(NaHCO3) etc.

Iron, copper, silver, gold

etc.

element and compounds

Documents