Exploring the Fascinating World of Elements: From Atoms to Nanotubes
Delve into the intricate realm of elements, where atoms and elements play a crucial role in our lives. Explore the significance of chemical symbols and the diverse forms of carbon such as graphite, diamond, Buckminsterfullerene, and nanotubes. Uncover the unique properties and potential practical uses of these elemental structures in various fields like medicine and technology.
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Course lecturer : Assist.Prof. Dr. Altijana Hromi -Jahjefendi
Book chapter: 4 Pages: 95-134
Contents 1. Atoms and Elements Forms of Carbon The PSE Atomic and Mass numbers Isotopes Electron energy levels Trends in PSE 2. 3. 4.
Atoms and Elements Elements are crutial for our lifes.... All matter is composed of elements Organic and anorganic matter is made of elements Essential for human health (I, Fe,Na,Mg, Ca, etc...)
Elements Elements are pure substances and cannot be broken down into smaller peaces! Names are give without specific rule (according place, planets,mystical places, famous people, colors, minerals...)
Chemical symbols One or two letter abbreviations for the names of the elements First letter is capitalized, second letter is lowercase to make the difference
If two letters are capiatlized symbol for two different elements (CO) Some symbols are derived from antient element names Example: Fe (iron) from Latin ferrum Na (sodium) from Latin natrium
Link to Environment Some elements have different forms Carbon (C) atoms can be arranged in different ways to give different substances Two forms of carbons: graphite and diamond In diamond, carbon atoms are arranged in rigid structure Transparent and harder than any other substance Graphite is black and soft; atoms arranged in sheets that slide over each other
Two other forms have been discovered recently Buckminsterfulleren or buckyball (R.Buckminster Fuller) 60 carbon atoms are arranged as rings of five or six atoms to give cage-like structrue When stretched out produces cylinder with diameter of only few nanometers Nanotube Practical uses are not yet developed Expect to find use in computer parts or medicine Can carry drug molecules that can be released once the CNTs enter the targeted cells
Link to Health Mercury is a silvery, shiny element Liquid at room temperature Can enter the body through inhaled mercury vapor, contact with the skin or ingestion of foods/water contaminated with mercury In body destroys proteins and disrupts cell function Long term exposure brain and kidney damage or decrease physical development
Bacteria in water convert mercury into toxic methylmercury Attacks CNS Fish absorbs methylmercury exposed to mercury by consuming contaminated fish Food and Drug Administration set a maximum level of one part mercury per million parts seafood (1 ppm) 1 mg of mercury/1 kg of seafood Higher food chain fish (shark or swordfish) can have higher levels of mercury Consumed no more than once a week 1950s Japan (Minamata and Niigata)
THE PERIODIC TABLE Arrangement of elements! Starting 1887 by Dmitry Mendelev with 60 elements. By the end of 2015, 118 elements are known.
Periods and Groups Horizontal row period Counted from the top of the table as Periods 1 to 7 Vertical column group Elements that have similar properties Representative elements had numbers 1A to 8A Transition elements had letter B Newer system assigns numbers of 1 to 18 to all of the groups from left to right across the PSE
Names of Groups Several groups have special names 1A alkali metals Li, Na, K, Rb, Cs and Fr Soft, shiny, good conductors of heat and electricity, low melting point React vigorously with water Form white products when they combine with oxygen
2A alkaline earth metals Not as reactive as 1A Be, Mg, Ca, Sr, Ba and Ra
7A halogens F, Cl, Br, I and At F and Cl are highly reactive Form compounds with most of the elements
8A noble gases He, Ne, Ar, Kr, Xe and Rn Quite unreactive Seldom found in combination with other elements
Metals, Nonmetals and Metalloids Zigzag line separating the elements into the metals and nonmetals Except of hydrogen, metals are to the left and nonmetals to the right
Most metals are shiny solids Cu, Au, Ag Can be shaped into wires or hammered into a flat sheet Good conductors of heat and electricity Melt at higher temperatures Solid at room temperature Exception: Hg (liquid)
Nonmetals are not specially shiny and ductile Often poor conductors of heat and electricity Low melting points and low densities Examples: H, C, N, O, Cl, S
Metalloids elements located on the heavy line B, Si, Ge, As, Sb, Te, Po and At Exception: Al Exhibit some properties of metals and some of nonmetals Better conductors of heat and electricity than nonmetals, but not as good as metals Semiconductors
Link to Health Essential elements make up 96% of our body H, C, N, O Macrominerals involved in formation of bones and teeth, maintenance of heart and blood vessels, muscle contraction Ca, P, K, Cl, S, Na, Mg Trace elements present in the body in very small amounts Zn, I
The Atome All the elements listed on the periodic table are made up of atoms. An atom - smallest particle of an element that retains the characteristics of that element
The concept of the atom is relatively recent Scientific theory became 1808 John Dalton developed an atomic theory Proposed that atoms were responsible for the combinations of elements found in compounds
Daltons Atomic Theory 1. All matter is made up of tiny particles called atoms. 2. All atoms of a given element are similar to one another and different from atoms of other elements. 3. Atoms of two or more different elements combine to form compounds. A particular compound is always made up of the same kinds of atoms and always has the same number of each kind of atom. 4. A chemical reaction involves the rearrangement, separation, or combination of atoms. Atoms are never created or destroyed during a chemical reaction.
Formed the basis of current atomic theory Now we know that atoms of the same element are not completely identical to each other Consist of even smaller particles However, still the smallest particle that retains the properties of an element Cannot be seen with the naked eye
The structure of an atom Electrons are negatively charged (e-) Protons are positively charged (p+) Neutrons are neutral Neutrons+protons are packed in atomic nucleus (center of the atom) Electrons move around the nucleus (nearly the speed of light)
Simplified models of an atom Cloud of negative charge (2 electrons) Electrons Nucleus (a) This model represents the electrons as a cloud of negative charge, as if we had taken many snapshots of the 2 electrons over time, with each dot representing an electron s position at one point in time. (b) In this even more simplified model, the electrons are shown as two small blue spheres on a circle around the nucleus. Figure 2.4
Atomic Number Atoms of the various elements differ in their number of subatomic particles All atoms of particular element have the same number of protons in nucleus Number of neutrons can vary Number of protons, which is unique to that element is atomic number Atoms are neutrally in charge! Means that number of protons is same as number of electrons Atomic number tells also number of electrons.
Mass number The mass number of an element Is the sum of protons plus neutrons in the nucleus of an atom Subtraction of atomic number from the mass number gives number of neutrons Example: Uranium atomic number=protons=92 mass number=protons+neutrons=235 neutrons=mass number-protons=143
Summary Elements and Symbols The periodic table Metals, Nonmetals and Metalloids Parts of atom
Isotopes Atoms of a given element may occur in different forms Some atoms have more neutrons than other atoms and therefore greater mass Those are called isotopes of the element Element occurs as mixture of isotopes in the nature Isotopes have slightly different mass but they behave identically in chemical reactions Example: Carbon
Isotopes 12C and 13C are stable isotopes-> their nuclei do not have tendency to loose particles 14C is unstable (radioactive) Radioactive isotope is one in which the nucleus decays spontaneously giving particles and energy Decay leads to change in the number of protons, it transforms the atom to an atom of a different element Useful application in biology: In fossils analysis Following atoms through metabolism Monitoring of biological processes (radioactive tracers in PET scan)
Can be used in biology Cancerous throat tissue
Electron energy levels Scientists have now determined that the lines in the atomic spectra of elements are associated with changes in the energies of the electrons. In an atom, each electron has a specificenergy known as its energy level, which is assigned values called principal quantum numbers (n) (n = 1, n = 2, n = 3,....)- up to 7 Energy levels makep up 4 orbitals (s, p, d and f) s has max 2e, p = 6, d= 10 and f=14
Electrons in lower energy level are closer to the nucleus Electrons in higher energy level are farther away All electrons with the same energy are grouped in the same energy level
Changes in electron energy level Am electron can change from one energy level to higher level Only if it absorbs energy equal to the difference in energy levels When it changes to a lower energy level it emits energy
Group number and Valence electrons The chemical properties of representative elements in Groups 1A (1) to 8A (18) are mostly due to the valence electrons, which are the electrons in the outermost energy level.
Group number gives the number of valence electrons for each group of representative elements 1 A one valence electron 7A seven valence electrons
Electron dot symbol Lewis representation Valence electrons are represented as dots when an atom has five to eight valence electrons, one or more electrons are paired
Atomic size The size of an atom is determined by the distance of the valence electrons from the nucleus. For each group of representative elements, the atomic size increases going from the top to the bottom because the outermost electrons in each energy level are farther from the nucleus
