Cơ sở hóa học

1
1
C S HÓA Ơ Ở
C S HÓA Ơ Ở
H C C A S Ọ Ủ Ự
H C C A S Ọ Ủ Ự
S NGỐ
S NGỐ

2
NỘI DUNG BÀI GIẢNG
NỘI DUNG BÀI GIẢNG

Vật chất, nguyên tố và nguyên tử
Vật chất, nguyên tố và nguyên tử

Cấu trúc nguyên tử
Cấu trúc nguyên tử

Liên kết hóa học
Liên kết hóa học

Tính chất hóa học của nước
Tính chất hóa học của nước

Axít, Bazơ và pH
Axít, Bazơ và pH


Cấu trúc và chức năng phân tử lớn
Cấu trúc và chức năng phân tử lớn

3
VẬT CHẤT
VẬT CHẤT

Vật chất là bất cứ vật gì có khối lượng và thể
Vật chất là bất cứ vật gì có khối lượng và thể
tích
tích

Hữu hình (Tangible)
Hữu hình (Tangible)

Có thể tồn tại dưới nhiều dạng
Có thể tồn tại dưới nhiều dạng

Rắn (Solid)
Rắn (Solid)

Lỏng (Liquid)
Lỏng (Liquid)

Khí (Gas)
Khí (Gas)

Plasma
Plasma


Bao gồm nhiều
Bao gồm nhiều
nguyên tố
nguyên tố

4
NGUYÊN TỐ
NGUYÊN TỐ

Một nguyên tố không thể phân chia thành các
Một nguyên tố không thể phân chia thành các
chất đơn giản bằng các phản ứng hóa học bình
chất đơn giản bằng các phản ứng hóa học bình
thường
thường

Có khoảng 100 nguyên tố khác nhau
Có khoảng 100 nguyên tố khác nhau

Mỗi nguyên tố có một ký hiệu nhất định
Mỗi nguyên tố có một ký hiệu nhất định

Ví dụ: Carbon (C), hydrogen (H), v.v.
Ví dụ: Carbon (C), hydrogen (H), v.v.

Nước (H
Nước (H
2
2

O), glucose, v.v không phải là nguyên tố.
O), glucose, v.v không phải là nguyên tố.

5
ELEMENTS
ELEMENTS

Có khoảng 25 nguyên tố cần thiết cho sự sống
Có khoảng 25 nguyên tố cần thiết cho sự sống

Gần 96% khối lượng vật chất sống là từ 4 nguyên
Gần 96% khối lượng vật chất sống là từ 4 nguyên
tố cơ bản
tố cơ bản

Carbon (C)
Carbon (C)

Hydrogen (H)
Hydrogen (H)

Nitrogen (N)
Nitrogen (N)

Oxygen (O)
Oxygen (O)

6
nguyên tử
nguyên tử


An
An
atom
atom
is the smallest unit into which an
is the smallest unit into which an
element can be subdivided while retaining its
element can be subdivided while retaining its
properties
properties

Comprised of smaller “subatomic” particles
Comprised of smaller “subatomic” particles

Protons
Protons
+ charge
+ charge
mass
mass
≈
≈
1 amu
1 amu

Neutrons
Neutrons

no charge
no charge
mass
mass
≈
≈
1 amu
1 amu

Electrons
Electrons
- charge
- charge
mass
mass
<<<
<<<
1 amu
1 amu
(1 atomic mass unit (amu)
(1 atomic mass unit (amu)
≈
≈
1 Dalton
1 Dalton
≈
≈
1.7 * 10
1.7 * 10
-24

-24
g)
g)

7
ATOMIC STRUCTURE
ATOMIC STRUCTURE

Protons and neutrons form an atom’s
Protons and neutrons form an atom’s
nucleus
nucleus

Electrons are present
Electrons are present
outside
outside
of the nucleus
of the nucleus

8
ATOMIC NUMBER
ATOMIC NUMBER

Atoms of different elements possess different
Atoms of different elements possess different
numbers of protons
numbers of protons

The

The
number of protons
number of protons
in an atom is termed its
in an atom is termed its
atomic number
atomic number

This number defines the element
This number defines the element

9
ATOMIC MASS
ATOMIC MASS

Protons and neutrons have significant mass
Protons and neutrons have significant mass

The
The
number of protons plus neutrons
number of protons plus neutrons
in an atom is
in an atom is
termed its
termed its
atomic mass
atomic mass

Electrons have negligible mass

Electrons have negligible mass

This number is slightly variable for many elements
This number is slightly variable for many elements

10
ISOTOPES
ISOTOPES

Isotopes
Isotopes
are atoms of the same element
are atoms of the same element
possessing different atomic masses
possessing different atomic masses

Due to different numbers of neutrons
Due to different numbers of neutrons

Identical chemical behavior
Identical chemical behavior

11
ISOTOPES
ISOTOPES

Some isotopes are stable
Some isotopes are stable

e.g.,

e.g.,
1
1
H,
H,
2
2
H,
H,
12
12
C,
C,
13
13
C, etc.
C, etc.

Some isotopes are unstable
Some isotopes are unstable

e.g.,
e.g.,
3
3
H,
H,
14
14
C,

C,
32
32
P,
P,
35
35
S, etc.
S, etc.

“
“
Radioactive”
Radioactive”

12
ISOTOPES
ISOTOPES

Radioactive isotopes
Radioactive isotopes

Decay at a constant rate into
Decay at a constant rate into
more stable forms
more stable forms

May decay into another element
May decay into another element


e.g.,
e.g.,
14
14
C
C


N
N

Various uses
Various uses

Important research tools
Important research tools

Monitor biological processes
Monitor biological processes

Diagnostic tools in medicine
Diagnostic tools in medicine

Determine age of fossils
Determine age of fossils

Sometimes produce superheroes
Sometimes produce superheroes

13

ISOTOPES
ISOTOPES

Each radioactive isotope has a fixed rate of decay
Each radioactive isotope has a fixed rate of decay

Unaffected by temperature, pressure etc.
Unaffected by temperature, pressure etc.

The time required for half of a sample to decay is
The time required for half of a sample to decay is
termed the radioisotope’s
termed the radioisotope’s
half-life
half-life

e.g., Half-life of
e.g., Half-life of
14
14
C is ~5,730 years
C is ~5,730 years

14
ISOTOPES
ISOTOPES

Fossils contain isotopes of elements that
Fossils contain isotopes of elements that
accumulated while they were alive

accumulated while they were alive

Accumulation stops upon
Accumulation stops upon
death
death

Death tends to reduce
Death tends to reduce
one’s appetite
one’s appetite

Accumulated isotopes
Accumulated isotopes
slowly decay into more
slowly decay into more
stable isotopes
stable isotopes

15
ISOTOPES
ISOTOPES

Ages of fossils can be determined using
Ages of fossils can be determined using
radiometric dating
radiometric dating

Compares accumulating “daughter” isotope to
Compares accumulating “daughter” isotope to

remaining “parent” isotope
remaining “parent” isotope

e.g., Carbon dating is useful for dating fossils up to
e.g., Carbon dating is useful for dating fossils up to
75,000 years old
75,000 years old

13 half-lives
13 half-lives

Radioisotopes with
Radioisotopes with
longer half-lives can
longer half-lives can
be used to date older
be used to date older
fossils
fossils

16
ELECTRON SHELLS
ELECTRON SHELLS

Electrons vary in the amount of energy they
Electrons vary in the amount of energy they
possess
possess

Each electron exists within a discrete

Each electron exists within a discrete
energy level
energy level

These energy levels are
These energy levels are
represented by
represented by
electron
electron
shells
shells

Most atoms possess
Most atoms possess
multiple electron shells
multiple electron shells

17
ELECTRON SHELLS
ELECTRON SHELLS

Electrons exist within electron shells
Electrons exist within electron shells

The first shell must be completely filled before
The first shell must be completely filled before
electrons are placed in the second shell, etc.
electrons are placed in the second shell, etc.


The first shell can hold 2 electrons
The first shell can hold 2 electrons

The next few electrons can each hold 8 electrons
The next few electrons can each hold 8 electrons

18
CHEMICAL BONDS
CHEMICAL BONDS

Atoms are most stable when their outermost
Atoms are most stable when their outermost
electron shell is completely full
electron shell is completely full

Making and breaking chemical bonds involves the
Making and breaking chemical bonds involves the
exchange or rearrangement of electrons
exchange or rearrangement of electrons

Atoms will tend to react such that their outermost
Atoms will tend to react such that their outermost
electron shell becomes completely full
electron shell becomes completely full

19
CHEMICAL BONDS
CHEMICAL BONDS
How would you expect F and Cl to react?
How would you expect F and Cl to react?

Li and Na?
Li and Na?
He, Ne, and Ar?
He, Ne, and Ar?

20
IONS
IONS

A sodium atom possesses a single electron in its
A sodium atom possesses a single electron in its
outermost electron shell
outermost electron shell

Tends to lose this electron
Tends to lose this electron

Loss of the electron
Loss of the electron
produces a sodium
produces a sodium
ion
ion

A charged form of a
A charged form of a
sodium atom
sodium atom

21

IONS
IONS

A chlorine atom possesses seven electrons in its
A chlorine atom possesses seven electrons in its
outermost electron shell
outermost electron shell

Tends to gain a single electron
Tends to gain a single electron

Gain of this electron produces a chloride ion
Gain of this electron produces a chloride ion

A charged form of
A charged form of
a chlorine atom
a chlorine atom

22
IONIC BONDS
IONIC BONDS

The attraction between oppositely charged ions is
The attraction between oppositely charged ions is
termed an
termed an
ionic bond
ionic bond


Compounds
Compounds
formed by ionic bonds are called “
formed by ionic bonds are called “
ionic
ionic
compounds
compounds
” or “
” or “
salts
salts
”
”

Indefinite size and number of ions
Indefinite size and number of ions

Ions present in a fixed ratio
Ions present in a fixed ratio

e.g., 1:1 ratio in NaCl
e.g., 1:1 ratio in NaCl

23
COVALENT BONDS
COVALENT BONDS

Electrons are not always gained or lost
Electrons are not always gained or lost


Molecules
Molecules
can be formed when electrons are
can be formed when electrons are
shared
shared

Sharing is always in pair(s) of electrons
Sharing is always in pair(s) of electrons

Shared electrons contribute to electron shells of both atoms
Shared electrons contribute to electron shells of both atoms

This sharing of electrons is termed a
This sharing of electrons is termed a
covalent bond
covalent bond

24
COVALENT BONDS
COVALENT BONDS

The sharing of a pair of electrons forms a
The sharing of a pair of electrons forms a
covalent bond
covalent bond

A
A

double covalent bond
double covalent bond
involves the sharing of
involves the sharing of
two pairs
two pairs
of electrons
of electrons

A
A
triple covalent bond
triple covalent bond


involves the sharing of
involves the sharing of
three pairs
three pairs
of electrons
of electrons

25
COVALENT BONDS
COVALENT BONDS

Electron sharing can be
Electron sharing can be
equal
equal

or unequal
or unequal

Equal sharing results in no separation of charges
Equal sharing results in no separation of charges

Nonpolar
Nonpolar
covalent bonds
covalent bonds