Chemistry project
On
Elements & compounds
DONE BY,
HABIBA TASKEEN
VI ‘A’
• 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
• 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 the
properties 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.
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%).
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
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 oxygen
elements 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 be
separated.
• 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
PREFIX OR MEANING EXAMPLE
SUFFIX
Mono- There is 1 atom of that type in that Carbon monoxide (CO)
molecule
Di- There are 2 atoms of that type in the Carbon dioxide (CO2)
molecule
Bi- Hydrogen is present in the molecule Sodium bicarbonate
(NaHCO3)
-ide There are only 2 types of atoms present Lead oxide
in the molecule
(PbO)
-ate There are 3 or more types of atoms in Calcium carbonate
the molecule, and 1 type is oxygen
(CaCO3)
VALENCY TABLE
• 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- PO4 3-
oxide phosphate
Na 1+ Ca 2+ Fe 3+ Cl 1- S 2-
Ferric sulphide
Li 1+ Cu 2+ Br 1- CO3 2-
carbonate
K 1+ Zn 2+ OH 1- SO4 2-
hydroxide sulphate
Ag 1+ Pb 2+ NO3 1-
nitrate
NH4 1+ Fe 2+ HCO3 1-
ammonium Ferrous bicarbonate
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 same
numbers at the bottom.
• Step 5 - If the numbers on each part are the same (e.g. Na1
Cl1 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).
CHEMICAL CHEMICAL NAME
EXAMPLES FORMULA
OF CO2 carbon dioxide
CHEMICAL CO carbon monoxide
NAMES OF Na Cl sodium chloride
Cu O copper oxide
Ag Br silver bromide
KI 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
COMPOUNDS
EXAMPLES OF NUMBERS AND TYPES OF ATOMS IN
VARIOUS ELEMENTS AND COMPOUNDS
NAME OF CHEMICAL ELEMENT OR NUMBER AND TYPE
FORMULA COMPOUND OF ATOMS IN MOLECULE
SUBSTANCE
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 atom
4 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
COMPARISON BETWEEN COMPOUNDS AND
ELEMENTS
Compound Element
A compound is a An element is a pure
Meaning. substance composed of chemical substance
two or more different made of same type of
chemical elements. atom.
Ability to Disintegrate A compound can be Elements cannot be
separated into simpler broken down into
substances by chemical simpler substances.
reactions.
Distinguishing Feature. Compounds contain Elements are
different elements in a distinguished by their
fixed ratio arranged in a atomic number (number
defined manner through of protons in their
chemical bonds. nucleus).
Representation A compound is An element is
represented using a represented using
formula. symbols.
Types. The list of compounds is There are about 117
endless but can broadly elements that have been
be classified as ionic and observed.
covalent.
Examples Sodium chloride (NaCl), Iron, copper, silver, gold
Sodium bicarbonate etc.
(NaHCO3) etc.
