ATOMS…

Atoms• Is the smallest particle characterizing a chemical

element.• Also defined as the smallest portion of an

element that retains all the properties of that element

• Coined from the Greek word Atomos—meaning “uncuttable”

• Consisits of a dense nucleus of positively charged protons

• And neutrons which are neutral• Surrounded by a much larger electron cloud –

negatively charged• Electrically neutral if protons=electrons• Protons defines the chemical element to which it

belongs• Neutrons determine the isotope

Dalton’s atomic theory

• All matter is composed of tiny, indivisible particles called atoms

• All atoms of an element are the same, but they differ from atoms of other elements

• Atoms of two or more elements combine to form compounds in ratios of simple whole numbers

• A chemical reaction involves a rearrangement of atoms

• Atoms cannot be created or destroyed• Note that all these have been updated

Atoms ctd

• Subatomic particles.• Though word atom originally denoted particle cannot be

cut into smaller particles.• In modern usage, atom is composed of various

subatomic particles which includes: electrons, protons and neutrons

• Electrons: This is a negatively charged particle and it is the smallest of the three types of atom. It revolves around the shell of atom, With a mass of 9.11*10

• Protons: This is a positively charged particle, free mass about 1839 times the mass of electron.

Atom ctd

• Neutrons: It has no charge, it is neutral. it has same size as proton. It has a free charge about 1839 times mass of electron.

• Protons and neutrons make up a dense, massive atomic nucleus.

• Are collectively called nucleolus.

• Electrons form the larger electron cloud surrounding the nucleus.

Protons and neutrons

Atoms ctd

• Atoms of same element have the same number of proton (called the atomic number) within single element, the number of neutrons may vary, determining the isotope of that element.

• The number of electrons associated with an atom is most easily charged, due to lower energy of binding of electrons

• Atoms are electrically neutral.i.e protons=neutral• Atoms with a deficit or surplus of electron are called ions.• Electrons that are furthest from nucleus may be

transferred to other nearby atoms or shared between atoms.

Atoms. (Ctd)

• By this mechanism, atoms are able to bond into molecules and other types of chemical compounds

• Molecules are made up of multiple atoms for e.g. water molecule is a combination of 2 hydrogen atoms one oxygen atom.

Atoms ctd

Isotopes

• Are any of the several different forms of an element

• Each having different mass number but same atomic number i.e same number of protons.

Periodic table.

Radioisotopes

• Radioactive isotopes are called radioisotopes or radionuclide.

• Is an atom with unstable nucleus• Nucleus with excess energy.• Excess energy is available to be imparted either

to a newly created radiation particle within nucleus or else to an atomic electron.

• Used for either its chemical properties or source of radiation.

Half life

• Half life of radioisotope is the time it takes half of the starting amount of the radioisotope to decay into something else.

• The decay is followed by release of various forms of radiation.

Electron shell

• Also known as the main energy level.• Electron shells are made up of one or

more electron sub shells or sublevels.• Electron shells make up the electron

configuration of an atom.• Valence shell is the outermost shell of an

atom in its uncombined site.• Valence electron dictates the nature of

reactions and bonding.

Electron shell

Avogadro’s number

• The number 6.0231023..• Indicating the number of atoms or molecules in a mole of

any substance.• mMol is one-thousandth of a mole.• Millimoles per liter unit of measurement showing

concentration of a substance in a specific amount of fluid.

• In most parts of the world, except U.S bld glucose test results are in mmol/l.

• In U.S milligrams per deciliter(mg/dl) is used• To convert mmol/l to mg/dl,divide mg/dl by 18• E.g. 180mg/dl divided by 18 is 10mmol/l

Chemical Bonding

• Atoms react with one another to form compounds

• Is associated with sharing or transfer of electrons between participating atoms.

• Resulting compound is unique chemically and physically from parent atoms

• Bonding makes atoms stable• Bonds vary widely in their strength and• Covalent and ionic bonds are strong while

hydrogen bonds are weak

Chemical bond ctd

Chemical bonds (ctd)

Covalent bonds

• Produced by electrical attraction produced when electrons are shared by 2 different atoms.

• The pair of electrons that hold the atoms together are called covalent bond

• An example is in the water molecule.

Covalent bond

Ionic bond

• One or more electrons are transferred from atoms of metal to atoms of non-metal.

• E.g in NaCl.

Cells.

• The structural and functional unit of all known living organisms.

• Some organisms are unicellular single cell) others are multicellular e.g. humans

• Cell theory developed by Matthias Jakob Schleiden’s and Theodore Schwann in 1839

• States that all organisms are composed of one or more cells. Also all cells come from pre-existing cells.

Cells (ctd)

• Vital functions of an organ occur within cells .• All cells contain hereditary information for

function and for transmitting information to the next generation of cells.

• Each cell is at least self-sustaining• Can take in nutrients convert the nutrient to

energy • Each cell stores its own set of instructions for its

own activity.• 2 types of cells • Eukaryotic and prokaryotic cell

Eukaryotic cells

• Usually found in multicellular organisms

• Found in animals,plants,fungi

• Specialized cells.

• Have a highly structured cytoplasm

• Several mitochondria

Prokaryotic cells

• Usually single cells

• Lack most intracellular organelles seen in eukaryotes except the ribosome

• Seen in bacteria

• No mitochondria

Prokaryotes

Eukaryotic and prokaryotic cells.

Cell membrane.

• Cell membrane-surrounds the cell.• Made of lipid and proteins.• Is semipermeable,allowing some substances,

excluding others.• Generally called the plasma membrane.• Major lipids are the phospholipids and

phosphotidylethanolamines.• There are different types of proteins.embedded

in the membrane.• They transport ions across the membrane.

nucleus

• Is made up of chromosomes largely.

• Chromosomes carry hereditary information for species.

• Each chromosome is made up of DNA

• Contains granules called nucleolus which contains the RNA.

mitochondria

• Sausage shaped structure

• Folded into cristae

• Is the power generating unit of the cell.

• Involved in synthesis of ATP

• Studded with enzymes involved in biologic oxidation.

• Complex structures

• Containing many different proteins.

• Consists of subunits called the 60s and 40s

• They are sites of protein synthesis.

Ribosome