preparatory program in basic science(ppbs001) part ii chemistry instructor: prof.dr.hassan...
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Preparatory Program in Basic Science(PPBS001)
PART II CHEMISTRY
Instructor: Prof.Dr.Hassan A.Mohammed
Syllabus:
The course will cover the following topics
CHAPTER (1 )
ATOMS & THE PERIODIC TABLE1.1 AtomsThe Smallest Building Blocks
The Atom’s Three Constituents
Charges within the Atom
The Atom is Mostly Empty
Distances inside the Atom
Atomic Number, Mass Number, and Atomic Mass
Masses within the Atom
Elements and Isotopes
1.2 The Periodic Table
Overview
Metals and Nonmetals
Metals
Nonmetals
Metalloids
Organization of the Periodic Table
Groups
Periods
References:1 -Hewitt Suchocki and Hewitt, Conceptual Physical Science.3rd
Ed, Pearson/Addison Wesley,2004
CHAPTER 2
COMPOUNDS& REACTIONSWhat Is Chemistry?
2.1 Physical & Chemical Properties
Physical PropertiesDescriptionChemical PropertiesDescriptionChemical ReactionsMolecules and CompoundsIons
14.1 The elements: Any material that is made up of only one type of atom
Examples: pure gold Au – Nitrogen gas N2- graphite(C atoms)1-All of the elements are listed in a chart called the periodic table.2- Each element is designated by its atomic symbol, which comes from the letters of the element's name. For example, the atomic symbol for carbon is C, and that for chlorine is Cl.
Chapter: 1Lecture.1:
The elements, atoms, protons and neutrons
The atom is the smallest amount of a pure material (or element. Thus, a gold atom is the smallest amount of gold we can possibly have. By small, we mean extremely tiny: a single atom is about 100,000 times thinner than a human hair, so the only way to see atoms is by using very powerful electron microscopes.
3-Elements having symbols derived from Latin names are usually those that were discovered earliest.Example: Pb (plumbum) is elder than calcium Ca Au(aurum) is elder than aluminum Al
4- Note that only the first letter of an atomic symbol is capitalized. The symbol for the element cobalt, for instance, is Co, while CO denotes a combination of two elements: carbon, C, and oxygen, O.
14.2 Atoms Are Ancient and Empty:
Atom:
The smallest particle of an element that has all of the element's chemical properties.
3-Atoms are so small that there are more than 10 billion trillion of them in each breath you exhale. If a typical atom were expanded to a diameter of 3 km, about as big as a medium-sized airport. the nucleus would be about the size of a basketball. Atoms are mostly empty space.
4-Atoms are so small that they can’t be seen with visible light that is because they are smaller than the wavelength of visible light
Atoms are dominantly empty space:
If an oxygen atom had a total
radius of 100 km, the nucleus would be a ~1 m diameter sphere
in the middle.
electron orbits
The Spacious Atom
5 -Today we know the atom is made up of smaller subatomic particles- electrons, protons, and neutrons. We also know that atoms differ from one another only in the number of these subatomic particles. Protons and neutrons are bound together at the atom's center to form the atomic nucleus. The nucleus is much smaller than the atom but it contains most of an atom's mass. Surrounding the nucleus are the tiny electrons as shown in figure
6- Electrons in the outer regions of an atom repel the electrons of neighboring atoms. Any two atoms, therefore, can get only so close to each other before repulsion dominates which keeps atoms from overlapping with one another.(A Puzzling Question)
14.3 Protons and Neutrons:
Let's take a closer look at the atom and investigate the particles found in the atomic nucleus. First, consider protons
A proton carries a positive charge and is relatively heavy-nearly-2.000 times as massive as the electron. The proton and electron have the same quantity of charge, but the opposite sign. The number of protons in the nucleus of any atom is equal to the number of electrons whirling about the nucleus. So the opposite charges of protons and electrons balance each other, producing a zero net charge. The atom is electrically neutral.
For example, an electrically balanced oxygen atom has a total of eight electrons and eight protons.
Scientists have agreed to identify elements by atomic number, which is the number of protons each atom of a given element contains.
Particle ChargeSymbol
Charge inElectron
Units
Charge inCoulombs
Proton Qp +1e 1.6021892 × 10-19 C
Electron Qe -1e -1.6021892 × 10-19 C
Neutron Qn 0 0
There is additional mass which is due to another subatomic particle found in the nucleus, the neutron. The neutron has about the same mass as the proton, but it has no electric charge.
ParticleMass
SymbolMass RelativeTo Electron’s
Maas inKilograms
Proton mp 1836 1.673 × 10-27 kg
Neutron mn 1841 1.675 × 10-27 kg
Electron me 1 9.11 × 10-31 kg
Atomic mass is measured by the atomic mass unit (amu), where 1 amu = 1.66×10-27 kg (slightly less than a nucleon’s mass).
Thus, in amu units, the value of the atomic mass (ma) is (approximately) equal to the mass number (A).
Example :
We saw earlier that Beryllium has 9 nucleons. This means that its ma = 9 amu = 14.94×10-27 kg. This value is slightly less than the sum of the masses of the nucleons: 4 mp + 5 mn = 15.07×10-27 kg.
Note: We saw in the last example that the sum of masses of the nucleons composing an atom is more than the atomic mass. This mass difference (Δm), called the mass defect, is a measure of the atom's binding energy, released during the formation of a nucleus from its composing nucleons.
Lecture.2 The periodic table, isotopes and atomic mass, Periods and groups
2.1 Isotopes and Atomic Mass
We identify an isotope by its mass number, which is the total number of protons and neutrons (nucleons) in the nucleus As Figure 1. shows, a hydrogen isotope with only one proton is called hydrogen-1(Protium), where 1 is the mass number. A hydrogen isotope with one proton and one neutron is therefore hydrogen-2(Deuterium), and a hydrogen isotope with one proton and two neutrons is hydrogen-3(Tritium).
Fe Atomic symbol 26
Atomic number
Mass number 56
Similarly, an iron isotope with 26 protons and 30 neutrons is called iron-56, and one with only 29 neutrons is iron-55.
The total number of neutrons in an isotope can be calculated by subtracting its atomic number from its mass number
Mass number – atomic number =Number of neutrons
26 protons30 neutrons
56 protons and neutrons
LecturePLUS Timberlake 21
More Atomic Symbols
163165 O P Zn
81530
8 p+15 p+30 p+
8 n16 n35 n8 e-15 e-30 e-
GROUP STUDY PROBLEM 1 .The element with atomic number 53 contains_______
a) 53 neutrons b) 53 protons C) 26 neutrons & 27 protons d) 26 protons & 27 neutrons
2. The mass of one atom of an isotope is 9.746 x 10-23 g. One atomic mass unit has the mass of 1.6606 x 10-24 g. The atomic mass of this isotope is _______
a) 5.870 amub) 16.18 amuc) 58.69 amud) 1.627 amu
108
_______ 3 .The number of neutrons in an atom of 47 Ag is
a) 47b) 108c) 155d) 61
27
_______ 4.The number of electrons in an ion of 13 Al3+ is
a) 13b) 10c) 27d) 14
5. What is the relative atomic mass of boron if two stable isotopes of boron have the following mass and abundance:
_______ 10.0129 amu (19.91%) & 11.0129 (80.09%)
a) 10.81 amub) 10.21 amu c) 10.62 amu d) 10.51 amu
Calculating Atomic Mass
To arrive at the atomic mass presented in the periodic table, you must first multiply the mass of each naturally occurring isotope of an element by the fraction of its abundance, and then add up all the fractionsExample: Carbon-12 has a mass of 12.0000 atomic mass units, and it makes up 98.89 percent of naturally occurring carbon. Carbon-13 has a mass of 13.0034 atomic mass units, and it makes up 1.11 percent of naturally occurring carbon. Use this information to show that the atomic mass of carbon shown in the periodic table, 12.011 atomic mass units, is correctAnswer :
Actual mass of C = (O.9889 x 12 )+ (o.o111x13.0034) =11.867 + o.144 = 12.011
Example :
Gallium is a metallic element found in small lasers used in compact disc
players. In a sample of gallium, there is 60.2% of gallium-69 (68.9 amu)
atoms and 39.8% of gallium-71 (70.9 amu) atoms .
What is the atomic mass of gallium?
Ga-69 (%/100)
68.9 amu x 60.2 = 41.5 amu for 69Ga
100
Ga-71 (%/100)
70.9 amu x 39.8 = 28.2 amu for 71Ga
100
Atomic mass Ga = 69.7 amu
LecturePLUS Timberlake 26
Copper has two isotopes 63Cu (62.9 amu) and 65Cu (64.9 amu). What is the % abundance of each isotope? (Hint: Check periodic table for atomic mass)
1 (30%2 (70%3 (100%
Solution
2 (70%
62.9X + 6490 = 64.9X + 6350
-2.0 X = -140
X = 70%
PRACTICE PROBLEMS # 81 . 1-A sample of neon contains three isotopes,
neon-20 (with an isotopic mass of 19.9924 amu), neon-21 (20.9939 amu) and neon-22 (21.9914 amu). The natural abundances of these isotopes are 90.92%, 0.257 %, and 8.82 %. Calculate the atomic weight of neon.
2 .There are only two naturally occuring isotopes of copper, 63Cu and 65Cu. Copper has an atomic mass of 63.55 amu. What is the natural abundance of each isotope?
3 .There are only two naturally occuring isotopes of gallium, 69Ga and 71Ga. What is the natural abundance of each isotope?
20.17 amu
65Cu = 30% & 63Cu = 70%
69Ga = 60% and 71Ga = 40%
14.5 The Periodic Table
The periodic table is a listing of all the known elements with their atomic symbols, atomic numbers, and atomic masses, But there is much more information in this table The organization of the table tells us a lot about the structures of the elements and how they behave For instance, let's look at the grouping of elements known as metals, nonmetals, and metalloids.
Most elements are metals which are defined as being shiny, opaque, and good conductors of electricity and heat. Metals are malleable, which means they can be hammered into different shapes or bent without breaking. They are also ductile, which means they can be drawn into wires. All but a few metals are solid at room temperature.
The exceptions include mercury, Hg ,gallium, Ga, cesium, Cs; and francium, Fr; which are all liquids at a warm room temperature of 30°C (86°F).
The nonmetallic elements, with the exception of hydrogen, are on the right of the periodic table Nonmetals are very poor conductors of electricity and heat, and most of them are also transparent. Solid nonmetals are neither malleable nor ductile. Rather, they are brittle and they easily shatter when harnmered: At 30°C (86°F), some non-.metals are solid (carbon, C), others are liquid (bromine, Br), and still others are gaseous
(helium,He).
Another interesting exception is hydrogen, H, which takes on the properties of a liquid metal only at very high pressures. Under normal conditions, however, hydrogen behaves as a nonmetallic gas.
Six elements are classified as metalloids: boron, B; silicon, Si; germanium, Ge; arsenic, As; antimony, Sb; and tellurium, Te. Situated between the metals and the nonmetals in the periodic table the metalloids have both metallic and characteristics. nonmetallic
For example, these elements are weak conductors of electricity, which makes them useful as semiconductors in the integrated circuits of computers. Note, from the periodic table, how germanium, Ge (number 32), - is closer to the metals than to the nonmetals.Because of this positioning, we can deduce that germanium has more metallic properties than silicon, Si (number 14), and is a slightly better conductor of electricity. So we find that integrated circuits fabricated with germanium operate faster than those fabricated with silicon. Because silicon is much more abundant and less expensive to obtain, however, silicon
computer chips remain the industry standard.
14.6 Periods and GroupsTwo other important ways in which the elements are organized in the periodic table are by horizontal rows and vertical columns. Each horizontal row is called a period. and each vertical column is called a group (or sometimes a family. As shown in Figure 3. there are 7 periods and 18 groups
In 1985, an international system was adopted in which the columns (or groups) in the periodic table are numbered 1-18.
Across any period, the properties of elements gradually
change. This graduate change is called a periodic trend.
As shown in Figure 3, one periodic trend is that atomic
size tends to decrease as you move from left to right
across any period. Note that the trend repeats from one
horizontal row to the next.
This phenomenon of repeating trends is called periodicity,
a term used to indicate that the trends recur in cycles.
Each horizontal row is called a period because it
corresponds to one full cycle
Shells for the First Three Periods
There are many other properties of elements that change gradually in moving from left to right across the periodic table. An important property is the ability of an atom to attract more electrons than it already has
• This property goes by the name electronegativity. As
shown in Figure 3, there is a periodic trend such that
elements to the lower left of the periodic table have the
smallest electronegativities, while elements to the upper
right (group 18 elements
excluded) have the largest electrongativities.
Down any group (vertical column), the properties of the
elements tend to be remarkably similar, which is why
these elements are said to be "grouped" or "in a family."
As Figure 3 shows, several groups have traditional
names that describe the properties of their elements.
Trend of electronegativity in the Periodic Table
Group 2 elements are known as the alkaline-earth metals. Over toward the right side of the periodic table, elements of group 16 are known as the chalcogens ("ore-forming" in Greek) because the top two elements of this group, oxygen and sulfur, are so commonly found in ores. Elements of group 17 are known as the halogens ("salt-forming" in Greek), because of their tendency" to form various salts. Interestingly, a small amount of the halogen iodine or the bromine inside a lamp allows the lamp's tungsten filament to glow more brightly without burning out so quickly halogen
Group 18 elements are all reactive gases that tend not to combine with other elements. For this reason, they are called the noble gases,
Br
The elements of groups 3 through 12 are all metals that do not form alkaline solutions with water. These metals tend to be 'harder than the alkali metals and less reactive with water, hence they are used for structural purposes. Collectively they are known as the transition metals, a name, that denotes their central position in the periodic table. The transition metals include iron (Fe), copper (Cu), nickel (Ni), chromium (Cr), silver (Ag), and gold (Au).
In the sixth period is a subset of 14 metallic elements (numbers 58 to 71) that are quite unlike any of the other transition metals. A similar subset (numbers 90 to 103) is found in the seventh period. These two subsets are the inner transition metals.
SUMMARY OF TERMS
Periodic Table: chart in which all known elements are listed in order of atomic number.Atomic Symbol: an abbreviation for an element or atomAtomic nucleus : The core of an atom, consisting of two basic subatomic particles- protons and neutronsElectron: A negatively charged particle in an atomProton: A positively charged particle in an atomic nucleusAtomic number : The number that designates the identity of an element, which is the number of protons in the nucleus of an atom;in a neutral atom, the atomic number is also the number of electrons in the atomMass number: The total number of nucleons in an atomic nucleus
Neutron : An electrically neutral subatomic particle in an atomic nucleusNucleon :A nuclear particle; a proton or neutron in an atomic nucleusIsotopes : Different forms of an element whose atoms contain the same number of protons but different numbers of neutronsAtomic mass : The mass of an element's atoms listed in the periodic table as an average value based on the relative abundance of the element's isotopesAtomic mass unit(amu) :The standard unit of atomic mass , which is equal to one-twelfth the mass of the common atom of carbon ,arbitrarily given the value of 12Period : A horizontal row in the periodic tableGroup: A Vertical row in the periodic table, also known as a family of elements
