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Course lecturer :

Jasmin Šutković

12th October 2015

Organic Chemistry – FALL 2015

Lecture 1:Atoms and the periodic table

What is Organic Chemistry ?????

Organic chemistry is that branch of chemistry that deals with the structure, properties, and reactions of compounds that contain Carbon!!

The study of molecules containing the carbon-hydrogen (C-H) bond and their reactions.

Organic Chemistry in every day life

What is Matter ?

Matter is anything that occupies space and possesses MASS. People, Gold, Smoke, Smog and so on….. NOT MATTER : light and sound! Many people mix-up MASS and Weight .

Object MASS is not its WEIGHT !!!

Mass VS. Weight

MASS is a measurement of the amount of matter something contains, while WEIGHT is the measurement of the pull of gravity on an object.

Matter does not depend on the location of an object but Weight does !!!

Example: On the Moon, your MASS will be the same, but your WEIGHT will be different since the Moon doesn't have the same gravity as the Earth.

States of Matter ?

Under normal conditions there are three distinct states of matter :1. Solids – rigid and fixes shape

2. Liquids – fixed volumes and take the shape of their containers

3. Gases – have neither fixed shape nor fixed volume and fill their container completely

Figure 3. Example of states of matter

Pure Substances and Mixtures

Pure Chemical Substance — any matter that has a fixed chemical composition and characteristic properties

Mixture — combinations of two or more pure substances in variable proportions in which the individual substances retain their identity

1. Homogeneous mixtures a. All portions of a material are in the same state, have no

visible boundaries b. Also called SOLUTIONS

2. Heterogeneous mixtures a. Composition of a material is not completely uniform

Most mixtures can be separated into pure substances - Elements or Compounds.

ELEMENTS is any substance that CANNOT be broken down into simpler substances .

Many definition of Elements exists but the modern one is :

An element is a substance that consists only of atoms with the same nuclear charge .

99.99% of all substances are made of only 40 elements .

COUMPOUNDS are substances that can be broken into two or more elements.

Properties of Matter

· Properties used to describe material substances can be classified as either physical or chemical.

· Physical properties:

Characteristics that scientists can measure without changing the composition of the sample under study (mass, color, volume, amount of space occupied by the sample).

· Chemical properties:

Describe the characteristic ability of a substance to react to form new substances (flammability and corrosion).

Measurement

SI Units

Système International d’Unités Uses a different base unit for each quantity

Metric System

In the United States, most measurements are made with the English system, using units like miles (mi), gallons (gal), pounds (lb), and so forth. A disadvantage of this system is that the units are not systematically related to each other and require memorization.

Scientists, health professionals, and people in most other countries use the metric system, with units like meter (m) for length, gram (g) for mass, and liter (L) for volume.

Measurement of mass , volume and length …find in page 9-11

Atoms and the periodic table

Contents International University of Sarajevo

Elements Elements in the periodic table The elements of life – human body Compounds

Structure of the ATOM Isotopes, atomic number and mass numberAtomic weightIsotopes in medicine –human health

The periodic table of elementsBasic features of the periodic tableCharacteristics of groups 1A, 2A, 7A and 8A

Electron configuration Electron configuration and the periodic system of elements

Electronic structure

Valence electrons

Elements

114 known, 90 naturally occurring and 24 are prepared by scientist in the lab

Named according people, places and things; Albert Einstain (Es – einstanium), California (Cf – californium) etc…

Elements are identified by one, two letter symbols

C (carbon) and Cl (Chlor)

International University of Sarajevo

Pure substances that cannot be broken down into simpler substances by a chemical reaction

Elements in the periodic table

Arrangements of elements into a table – periodical table of elements!

The position of element in PT (periodic table) tells us much about its chemical properties !

The elements in PT are divided into 3 groups:

1. Metals (left of the line in PT)

2. Nonmetals (right of the line in PT) except Hydrogen

3. Metaloids (along the border of metals and nonmetals)

Periodic table of Elements

The elements of life – human body

Human body is composed of Carbon, oxygen, hydrogen and nitrogen – 96% - called the building block elements !

H + O form water – the most prevalent substance in our body

C, H and O are found in four main types of biological molecules :

proteins, carbohydrates, lipids and nucleic acids

Seven other elements are called major elements or macronutrients ( 0.1-2 %) – daily 100 mg need! Magnesium (Mg) and Sulfur (S) are occur in proteins Sodium (Na),Potassium(K) and Chlorine(Cl) are found in body

fluids Phosphorus (F) is found in nucleic acids

Other elements occur in small amounts but essential for our body – micronutrients. Required for daily diet in small quantities (15 mg) Iron (Fe) – carries oxygen in red blood cells (hemoglobin) Zinc (Zn) – helps liver and kidney to function Iodine(I) - needed for thyroid to function

The elements of life

Compounds

Pure substances formed by chemically combining 2 or more elements.

Element symbols are used to write chemical formulas for compounds.

A chemical formula uses element symbols to show the identity of the elements forming a compound and subscripts to show the ratio of atoms (the building blocks of matter) contained in the compound.

Example

Example 2 – ball and stick model

Structure of the Atom

All matter is composed of the same basic building blocks called atoms.

An atom is composed of three subatomic particles:

• A proton, symbolized by p, has a positive (+) charge.

• An electron, symbolized by e–, has a negative (–) charge.

• A neutron, symbolized by n, has no charge.

Atom components

Every atom of a given type of element always has the same number of protons in the nucleus, a value called the atomic number, symbolized by Z. Conversely, two different elements have different atomic numbers.

Z = the number of protons in the nucleus = the number of electrons.

Thus the atomic number tells us both the number of protons in the nucleus and the number of electrons in the electron cloud

Caffeine example

Isotopes

Two atoms of the same element always have the same number of protons but the number of NEUTRON may differ!

Thus Isotopes are atoms of the same element having different number of neutrons .

Most elements in nature exists as a mixture of isotopes !

Example : Hydrogen has 3 isotopes

Isotopes in medicine

Generally the chemical properties of isotopes are identical. Sometimes, however, one isotope of an element is radioactive, it emits particles or energy as some form of radiation. Radioactive isotopes have both diagnostic and therapeutic uses in medicine.

As an example, iodine-131 is used for thyroid disease. Iodine is a micronutrient needed by the body to synthesize the thyroid hormone thyroxine, which contains four iodine atoms.

Higher doses of iodine-131 can also be used to treat thyroid disease. Since the radioactive isotope is taken up by the thyroid gland, the radiation it emits can kill overactive or cancerous cells in the thyroid.

Atomic weight

Also Known As: Atomic Mass

The periodic table

Read and study by yourself , the book page 44-48

Electron structure

The chemistry of an element is determined by the number of electron in an atom.

Modern description :

The farther a shell is from the nucleus, the larger its volume becomes, and the more electrons it can hold. Thus, the first shell can hold only two electrons, the

second holds eight, the third 18, and so forth.

The electrons that surround a nucleus are confined to regions called the principal energy levels, or shells.

Shells are divided into subshells, identified by the letters s, p, d, and f. The subshells consist of orbitals.

An orbital is a region of space where the probability of finding an electron is high. Each orbital can hold two electrons.

The first shell of electrons around a nucleus (n = 1) has only one s orbital. This orbital is called the 1s orbital since it is the s orbital in the first shell. Since each orbital can hold two electrons and the first shell has only one orbital, the first shell can hold two electrons.

Orbital's and Electrons Contained in the Principal Energy Levels (n = 1–4)

Electron configuration

What is the electron configuration of iron?

Iron's atomic number is 26. Thus it has 26 protons and 26 electrons. The electronic configuration for the first 26 electrons, and so therefore iron, is Fe

1s2 2s2 2p6 3s2 3p6 4s23d6. 

VALENCE ELECTRONS

The chemical properties of an element depend on the most loosely held electrons—that is, those electrons in the outermost shell, called the valence shell. The period number tells the number of the valence shell.

The electrons in the outermost shell are called the valence electrons.

The Group number of a non-transition metal indicates the number of valence electrons.

Group 1: 1 valence electron Group 2: 2 valence electrons Group 13: 3 valence electrons Group 14: 4 valence electrons Group 15: 5 valence electrons Group 16: 6 valence electrons Group 17: 7 valence electrons Group 18: 8 valence electrons -- except for helium, which has 2

Examples

ELECTRON-DOT SYMBOLS

The number of valence electrons around an atom is often represented by an electron-dot symbol.

Representative examples are shown.

Periodic trends

Many properties of atoms exhibit periodic trends; that is, they change in a regular way across a row or down a column of the periodic table. Two properties that illustrate this phenomenon are atomic size and ionization energy.

ATOMIC SIZE

The size of an atom is measured by its atomic radius—that is, the distance from the nucleus to the outer edge of the valence shell. Two periodic trends characterize the size of atoms.

The size of atoms increases down a column of the periodic table, as the valence electrons are farther from the nucleus.

IONIZATION ENERGY

Since a negatively charged electron is attracted to a positively charged nucleus, energy is required to remove an electron from a neutral atom.

The more tightly the electron is held, the greater the energy required to remove it.

Removing an electron from a neutral atom forms a cation.

That’s it for this chapter .. …

Link for Book download: https://drive.google.com/file/d/0B1lV-EMiZm99clo4SndHTEFUZW8/view?usp=sharing   

Syllabi and Lecture 1 available at IUS web page; Academic: Jasmin Sutkovic, Resources