Lecture 2 Flashcards
(24 cards)
What is Daltons Atomic Theory
All matter is made up of atoms
Atoms of the same element are identical however difference to atoms from other element
Compounds - combo of 2 or more different elements
In chem reactions- atoms are combined, separated or rearranged
Atoms are never created or destroyed
Molecules what are they
Electrically neutral group of two or more atoms.
Can be of the same or different non metal elements- held together by covalent bonds
O2 - 2 atoms of oxygen
H2 - 2 atoms of hydrogen
H2O - 2 hydrogen and 1 oxy
CO2 - 1 carbon and 2 oxygen
What value is noted as subscript?
Atoms/elements present in numbers greater than 1
Atoms what are they
Have a single nucleus and its electron cloud
Electrons in the outer shell are involved in the reaction of atoms
The outermost shell of an atom in its uncombined state – Valence (electrons) shell involved in reactions
Every element within a group has the same number of valence electrons Corresponds to the group number 2, 8, 8, 2
Ions what are they
An atom containing an equal number of protons and electrons is electrically neutral
Ions are atoms that have acquired a net positive or negative charge by loosing or gaining valence electrons
Ions are expressed as the symbol/element with a superscript, showing the magnitude and sign of the charge eg NA+, CA2+
Cation
Loss of electron – convert the atom to a positive ion
Number of protons greater than the number of electrons
Anion
Gain of electron —— convert the atom to a negative ion
Ionization
An atom gain or loose electrons to create a stable outer valence shell ( ionization)
When the electron shell is filled with electrons then the element is stable and unreactive
Bohr Model
Shows all the electrons in the shells
Positively charged ion
Lose electrons when 1, 2 or 3 electrons are in the outer valence shell usually metals. Note these electrons also denote electron groups
Negatively charged ion
Gain electrons when 6 or 7 electrons are in the outer valence shell usually nonmetals
ionic bond
An ionic bond is a chemical bond that involves a metal and a nonmetal ion
Atoms either losing or gaining negatively charged electrons, reacting to form ions
Positive ions (metals) are attracted to negative ions (nonmetals)
In naming simple ionic compounds, the metal (cation) is always first, the nonmetal (anion) second
Lewis Dot Structure
Similar to the Atomic Structure – except only the valence shell is shown
Indicated by dots
Sometimes referred to as the electron dot structure
Characteristics of plasticware
Cheaper and more durable (unbreakable). lightweight and impact- and corrosion-resistant
Disadvantage – some leaching of surface bound constituents into solutions and evaporation through plastic
Characteristics of Glassware
Frequently preferred for analytical work because of it’s chemical stability and clarity
Special types of glass have been devised for special use
flint glass/soda lime, borosilicate glass, or quartz/silica glass
Polyethylene
used for graduated cylinders
Polystyrene
petri dish, test tubes
Polypropylene
milky or opaque appearance and are heat resistant
Flint glass (soda lime):
Inexpensive, low resistance to heat and chemicals. Used to make disposable test tubes
Borosilicate glass
Nonreactive with most chemicals, high thermal (heat) resistance glassware
Used for most lab glassware, Pyrex and Kimax
Quartz/Silica glass:
Very expensive, contains only silica quartz with excellent optical qualities
Used for high precision work – spectrophotometry cuvettes, microscope lens
Volumetric pipette
Used for critical/accurate measurements
Calibrated to deliver “TD” a single volume
Has a bulged out portion (bulb) in the middle
Serological/Graduated pipette
Calibration marks to the tip
Etched ring around the top – last drop must be blown out
Mainly used for preparing serial dilutions
Transfer total capacity or partial volumes
Mohr pipette
Not calibrated to the tip
Do not drain beyond last calibration marking
