CHAPTER-1 BASIC CONCEPTS OF CHEMISTRY Chemistry is a branch of science that involves the study of the composition, structure and properties of matter. Chemistry is important because everything you do is chemistry! Even your body is made of chemicals. Chemical reactions occur when you breathe, eat, or just sit there reading. All matter is made of chemicals, so the importance of chemistry is that it's the study of everything Matter is anything that has mass and takes up space. Matter requires at least one subatomic particle, although most matter consists of atoms. States of Matter- There are 3 States of Matter. Solids, Liquids and Gases • Some Characteristics of Gases, Liquids and Solids – Solid matter is composed of tightly packed particles. A solid will retain its shape; the particles are not free to move around. – Liquid matter is made of more loosely packed particles. It will take the shape of its container. Particles can move about within a liquid, but they are packed densely enough that volume is maintained. – Gaseous matter is composed of particles packed so loosely that it has neither a defined shape nor a defined volume. A gas can be compressed. • S.I UNITS - The units and their physical quantities are the second for time, the metre for measurement of length, the kilogram for mass, the ampere for electric current, the kelvin for temperature, the mole for amount of substance, and the candela for luminous intensity. Some important SI Units • Derived SI Units with Special Names • Frequency v, hertz • force F newton • pressure p pascal
28
Embed
CHAPTER-1 BASIC CONCEPTS OF CHEMISTRY - Lisana · BASIC CONCEPTS OF CHEMISTRY Chemistry is a branch of science that involves the study of the composition, structure and properties
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
CHAPTER-1
BASIC CONCEPTS OF CHEMISTRY
Chemistry is a branch of science that involves the study of the composition,
structure and properties of matter.
Chemistry is important because everything you do is chemistry! Even your
body is made of chemicals. Chemical reactions occur when you breathe, eat,
or just sit there reading. All matter is made of chemicals, so the importance
of chemistry is that it's the study of everything
Matter is anything that has mass and takes up space. Matter requires at least
one subatomic particle, although most matter consists of atoms.
States of Matter- There are 3 States of Matter. Solids, Liquids and Gases
• Some Characteristics of Gases, Liquids and Solids
– Solid matter is composed of tightly packed particles. A solid will
retain its shape; the particles are not free to move around.
– Liquid matter is made of more loosely packed particles. It will take
the shape of its container. Particles can move about within a liquid,
but they are packed densely enough that volume is maintained.
– Gaseous matter is composed of particles packed so loosely that it
has neither a defined shape nor a defined volume. A gas can be
compressed.
• S.I UNITS - The units and their physical quantities are the second for
time, the metre for measurement of length, the kilogram for mass, the
ampere for electric current, the kelvin for temperature, the mole for
amount of substance, and the candela for luminous intensity.
Some important SI Units
• Derived SI Units with Special Names
• Frequency v, hertz
• force F newton
• pressure p pascal
• Energy joule
• Power P watt
• electric charge Q coulomb
Elements - Elements are chemically the simplest substances and hence
cannot be broken down using chemical reactions. An element is a substance
that is made entirely from one type of atom.
DIFFERENCE B/W COMPOUNDS AND MIXTURE
Compounds 1. Compounds are pure substances.
2. They are made up of two or more elements combined chemically.
3. The constituents of a compound are present in a fixed ratio.
4. Compounds have fixed properties. For example, a particular compound
will have fixed temperatures at which it melts and boils.
5. A compound can have properties different from its constituents, as a new
substance is formed when the constituents are chemically combined.
6. The constituents of a compound can be separated only by chemical
methods.
Mixtures
1. Mixtures are impure substances.
2. They are made up of two or more substances mixed physically.
3. The constituents of a mixture are present in varying ratios.
4. Mixtures do not have fixed properties. Their properties depend on the nature
of their components and the ratios in which they are combined.
5. In mixtures, no new substance is formed. The properties of a mixture are the
same as the properties of its constituents.
6. The constituents of a mixture can be separated easily physically.
SYMBOLS - A chemical symbol is a shorthand method of representing an
element. Instead of writing out the name of an element, we represent an
element name with one or two letters.
1. Tin- Sn
2. Lead- Pb
3. Gold- Au
4. Sulfur- S
5. Mercury- Hg
6. Silver- Ag
7. Iron- Fe
MOLECULAR FORMULA - A molecular formula consists of the
chemical symbols for the constituent elements describing the number of
atoms of each element present in the molecule.
EXAMPLE AgI silver iodide
Al2O3 aluminium oxide
BaCl2barium chloride
KBr potassium bromide
MgBr2 magnesium bromide
NaBr sodium bromide
NaI sodium iodide
ammonium chloride NH4Cl
sodium chloride NaCl
potassium chloride KCl
potassium nitrate KNO3
calcium hydroxide Ca(OH)2
Calculation of Molecular weight- Add atomic weight of all atoms present in
the molecular formula. Ex. H2O
H=1, O=16
2*1+16=18 amu
NaOH =23+16+1=40
CHAPTER-2
ATOMIC STRUCTURE
• An atom itself is made up of three tiny kinds of particles called
subatomic particles: protons, neutrons, and electrons. The protons and the
neutrons make up the center of the atom called the nucleus and the
electrons revolve around above the nucleus in a small cloud.
• An atom is the smallest constituent unit of ordinary matter that constitutes
a chemical element.
Electron,Proton and Neutrons
• Electron was discovered by J. J. Thomson in 1897.
• In 1909, Rutherford discovered proton in his famous gold foil
experiment.
• Atomic mass = mass of protons + mass of neutron.
• For a neutral atom, number of proton=number of electron.
• Measured masses and charges of the three elementary particles are given
in the following table.
• Particle Symbol Charge
• Electron e–
-1.60×10-19
C
• Proton p+ (H
+) 1.60×10
-19 C
• Neutron n0
0.00 C
Atomic representation
Z is used to signify the atomic number of an atom. Z = # of protons of an
atom. A is used to signify the atomic mass number (also known as atomic
mass or atomic weight) of an atom. A = # protons + # neutrons
Elements are represented by a chemical symbol, with the atomic number and
mass number sometimes affixed as indicated below. The mass number is the
sum of the numbers of neutrons and protons in the nucleus.
Bohr’s Atomic Theory
According to Bohr's theory , electrons revolve in definite circular orbits
around the nucleus and these orbits are designated by the letters K, L, M, N
or by the numbers 1, 2 ,3, 4 and so on.
• As long as the electrons revolve in a particular orbit they can neither gain
energy nor loose energy. Such orbits are called as stationary orbits or
stationary states.
• When an electron jumps from an higher orbit to a lower orbit it releases
energy in the form of radiations and when an electron jumps from lower
orbit to a higher orbit it absorbs energy in the form of radiations.
• The angular momentum of aln electron is an integral multiple of h/ 2π
mvr = nh/ 2π
• It explains the stability of an atom and also the line spectrum of hydrogen
atom.
Isotopes, Isobars and Isotones
Isotopes are two or more elements having the same number of protons but
different number of neutrons i.e having the same atomic number but
different mass number. Carbon 12 and Carbon 14 are both isotopes of carbon
Isobars are the elements having same mass number but different atomic
number. Eg. 40
S, 40
Cl, 40
Ar, 40
K, and 40
Ca.
Isotones are the elements that are having the same number of neutrons.
Aufbau Principle - The aufbau principle states that in the ground state of an
atom or ion, electrons fill atomic orbitals of the lowest available energy
levels before occupying higher levels. For example, the 1s subshell is filled
before the 2s subshell is occupied.
Hund's rule: every orbital in a subshell is singly occupied with one electron
before any one orbital is doubly occupied, and all electrons in singly
occupied orbitals have the same spin.
The Pauli Exclusion Principle states that no two electrons can have the
same quantum number, and thus, electrons in the same orbital must have
opposite spins.
Electron configuration- the electron configuration is the distribution of
electrons of an atom or molecule (or other physical structure) in atomic or
molecular orbitals.We follow the three important rules: Aufbau's Principle,
Pauli-exclusion principle, and Hund's Rule.
Some important electron configuration
Hydrogen (1H) – contains one electron. This electron will be
accommodated in the s orbital of K shell. Therefore, the accommodation
of this electron is written as 1s1 . The number before the orbital indicates
the main energy level the orbital is. The superscript is the number of
electrons accommodated by the orbital.
• the configuration of Li: 1s22s
1
• The electronic configuration of sodium is : 1s22s
22p
63s
1.
• the electronic configuration of K is 1s22s
22p
63s
23p
64s
1.
• Calcium (20Ca) – 1s22s
22p
63s
23p
64s
2
CHAPTER-3
CHEMICAL BONDING
A chemical bond is a lasting attraction between atoms, ions or molecules
that enables the formation of chemical compounds. The bond may result
from the electrostatic force of attraction between oppositely charged ions as
in ionic bonds or through the sharing of electrons as in covalent bonds.
Why do atoms combine?
Atoms combine together to lose their energy. This would make them stable.
Why do certain atoms combine while others do not?
This is mainly because a compound forms only when there is an attractive
force leading to the lowering of energy. On the other hand, in case of a
repulsive force, we find an increase in overall energy of the system. Thus,
we do not see the formation of any compounds.
Valence electron is an outer shell electron that is associated with an atom,
and that can participate in the formation of a chemical bond
In the Lewis symbol for an atom, the chemical symbol of the element (as
found on the periodic table) is written, and the valence electrons are
represented as dots surrounding it. Only the electrons in the valence level are
shown using this notation.
Octet rule - it states that every atom wants to have eight valence electrons in
its outermost electron shell. The octet rule explains how atoms of different
elements combine to form molecules. In a chemical formula, the octet rule
strongly governs the number of atoms for each element in a molecule; for
example, calcium fluoride is CaF2 because two fluorine atoms and one calcium
satisfy the rule.
Difference b/w orbit and orbital
An orbit on the other hand is simply present in a body with a certain mass,
while an orbital exists for an electron as well as an atom.
An orbit is the simple planar representation of an electron. An orbital refers
to the dimensional motion of an electron around the nucleus in a three
dimensional motion.
Electrovalent bonding - Electrovalent bonding or ionic bonding involves
the transfer of electrons between atoms. In such cases, one atom loses an
electron and the other atom gains an electron.When an electron transfer
occurs, one atom has a negative charge making it the anion. On the other
hand, the other atom has a positive charge making it the cation. The ionic
bond is majorly strong because of the concept of “opposite charges
attract.”
Covalent bonding - Covalent bonding is the most common method of
bonding in compounds containing carbon. These are basically the organic
compounds. A Covalent bond signifies the sharing of electrons between
atoms. In such cases, we know that there is a formation of a new orbit by
the shared pair of electrons. This orbit extends around the nuclei of both
the atoms and creates a new molecule.
Ionic Bonds Vs Covalent Bonds
Ionic Bonds Covalent Bonds
1 An ionic bond is formed
between a metal and a non-
metal. Non-metals(-ve ion)
are "stronger" than the
metal(+ve ion) and can get
electrons very easily from
the metal. These two
opposite ions attract each
other and form the ionic
bond.
Sodium chloride (NaCl),
Sulphuric Acid (H2SO4 )
Covalent bonding is a form of chemical bonding between two non metallic
atoms which is characterized by the sharing of pairs of electrons between