unit 1 matter and bonding
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Unit 1 Matter and Bonding. CHEMISTRY. Why do I have to study chemistry?. Atomic Theory. All elements are composed of atoms Each element contains similar atoms Atoms of one element are different from ones from another Two or more different atoms bond together to form a compound. - PowerPoint PPT PresentationTRANSCRIPT
Unit 1Matter and Bonding
CHEMISTRY
Why do I have to study chemistry?
Atomic Theory
All elements are composed of atoms
Each element contains similar atoms
Atoms of one element are different from ones from
another
Two or more different atoms bond together to form a
compound
Subatomic Particles
Particle Symbol Charge RelativeMass (u)
Electron e- -1 ~0
Proton p+ +1 1
Neutron n 0 1
Location of Subatomic Particles
10-15 m
electrons
protons
neutrons
10-10 m
nucleus
Characteristics of Electrons
Extremely small mass
Located outside the nucleus
Moving at extremely high speeds in defined
areas around the nucleus called orbitals
Have specific energy levels
In a neutral atom the # of electrons equals
the # of protons
Elements
Are pure substances that cannot be separated into different substances by ordinary processes
Are the building blocks of matter
All atoms of an element have the same number of protons
118 elements known todayExamples: carbon
nitrogengold
Liquid nitrogen.
Name the element found in each!
2.
4. Copper 5. Sulfur 6. Iodine
1. Carbon 2. Sodium 3. Aluminum
Symbols of Elements
Use 1 or 2 letter abbreviations Capitalize the first letter only
Examples:
C carbon Co cobalt
P Phosphorus Ca calcium
Ba Barium Mg magnesium
Symbols from Latin Names
Element Symbol Latin nameCopper Cu cuprum
Gold Au aurum
Lead Pb plumbum
Mercury Hg hydrargyrum
Potassium K kalium
Silver Ag argentum
Sodium Na natrium
Tin Sn stannum
Diatomic elements
• Some elements are composed of two atoms bonded together
• Whenever you write the symbol for these elements a subscript must be written
• Oxygen O2
• Nitrogen N2
• Chlorine Cl2
• Iodine I2
The Periodic Table
Represents physical and chemical behavior
of elements
Arranges elements by increasing atomic
number
Repeats similar properties in columns known
as chemical families or groups
Groups of Elements
Vertical columns on the periodic table
Similar physical properties
Similar chemical properties
Representative Groups
Group 1 Alkali Metals
Group 2 Alkaline Earth Metals
Group 17 Halogens
Group 18 Noble Gases
Periods on the Periodic Table
Horizontal rows from Group 1 to Group 18.
Numbered 1, 2, 3, ….
Metals- General properties
Located on the left hand side Usually solids Lustrous, ductile, malleable Good conductors of heat and electricity Group 1 and 2 metals react with oxygen to form
metal oxides which can react with water to from bases (alkaline)
Transition metals vary in reactivity, typically hard, high melting points, good conductors of electricity, form ions of variable charge
Non-metals: General properties
Located on the right hand sideCan be solid (S, P,C) liquid (Br2 at room
temperature) or gaseous (O2, F2)Dull and brittle solidsPoor conductors, good insulatorsHalogens are extremely reactiveNobel gases extremely unreactive, but
Xe, Kr, Rn will react reluctantly with F
Metalloids
• Do not fit the standard definition of metals or nonmetals
• Include: Boron, Silicon, Antimony, Germanium, Arsenic, Tellurium
• Located on the “staircase” of the periodic table
Metals and Nonmetals
NONMETALS
METALS
METALS
Transition Metals
Atomic Notation
• Atomic number: The number of protons in the nucleus of an element (smaller number)
• Mass number: The average atomic mass of an element (larger number)
Atomic Symbols
Show the mass number and atomic number
Give the symbol of the element
mass number
23 Na sodium-23
atomic number 11
More Atomic Symbols
16 31 65
O P Zn
8 15 30
__p+ __p+ __p+
__n __ n __n__e- __ e- ___ e-
Energy of Electrons
Electrons in atoms are arranged in levels.
An electron absorbs energy to “jump” to a
higher energy level.
When an electron falls to a lower energy level,
energy is released.
Energy levels are like using a stick shift in a car. The faster you travel the higher gear you use.
The Bohr Model
• First model made to illustrate electron structure
• Provides levels where an electron would most likely to be found
A Bohr model of Nitrogen.
Electron Levels (Shells)
Contain electrons that are similar in energy and
distance from nucleus
Low energy electrons are closest to the nucleus
Higher energy electrons are farther away from the
nucleus
The first shell (1) is lowest in energy, 2nd level
next and so on 1<2<3<4
Many shells also have sublevels
Number of Electrons per shell
Use the formula 2n2, where n is equal to the energy level
n =1 2(1)2 = 2
n =2 2(2)2 = 8
n =3 2(3)2 = 18
Periodic Law
All the elements in a group have the same electron configuration in their outermost shells
Example: Group 2
Be 2, 2
Mg 2, 8, 2
Ca 2, 2, 8, 2
Bohr and Lewis Review
Valence Electrons:
•Electrons with the greatest energy
•Electrons that will react to form compounds
Draw the Bohr Diagram for Al
Draw the Lewis Diagram for O
Draw the Lewis Diagram for the compound formed between Al and O. Name it.
Isotopes
Atoms with the same number of protons,
but different numbers of neutrons.
Atoms of the same element (same atomic
number) with different mass numbers
Isotopes of chlorine
35Cl 37Cl17 17
chlorine 35 chlorine 37
Radioisotopes
• An isotope of an element that is capable of spontaneously emitting radiation in the form of particles and/or gamma rays
• Occur naturally or can be produced artificially
• Ex: Tritium 31H
• Half Life: The time it takes for one 1/2 the nuclei in a radioactive sample to decay
• Uses: Nuclear power, cancer treatment carbon -14 dating
Masses of Atoms
A measuring unit designed for atoms gives
their atomic masses in atomic mass units (u)
An atom of 12C was assigned an exact mass of
12.00 u
The relative masses of all other atoms was
determined by comparing each to the mass of 12C
An atom twice as heavy as 12C has a mass of
24.00 u. An atom half as heavy is 6.00 u.
Atomic Mass
Listed on the periodic table
Gives the mass of “average” atom of each
element compared to 12C
Average atom based on all the isotopes and their
abundance %
Atomic mass is not a whole number
Na22.99
Calculating Atomic Mass
Percent(%) abundance of isotopes
Mass of each isotope of that element
Weighted average =
mass isotope1(%) + mass isotope2(%) + …
100 100
Atomic Mass of Magnesium
Isotopes Mass of Isotope Abundance 24Mg = 24.0 u 78.70%
25Mg = 25.0 u 10.13%
26Mg = 26.0 u 11.17%
Atomic mass (average mass) Mg = 24.3 u
Mg24.3
Learning Check!
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 u) atoms and 39.8% of
gallium-71 (70.9 u) atoms. What is the
atomic mass of gallium?
Finding An Isotopic Mass
A sample of boron consists of 10B (mass 10.0 u) and 11B (mass 11.0 u). If the average atomic mass of B is 10.8 u, what is the % abundance of each boron isotope?