Ch 2 - Atoms and Elements Flashcards
Law of Conservation of Mass
Antoine Lavoisier
In a chemical reaction matter is neither created or destroyed.
Law of Definite Proportions
Joseph Proust
All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements.
H20 is H20 everywhere in the world.
2:1 ratio
Law of Multiple Proportions
John Dalton
When two elements (A and B) form two different compounds, the masses of element B that combine with 1g of element A can be expressed as a ratio of small whole numbers.
Atomic Theory
John Dalton
1 - Each element is composed of tiny indestructible particles called atoms.
2 - All atoms of the same element have a given mass and other properties that distinguish them from the atoms of other elements.
3 - Atoms combine in simple, whole number ratios to form compounds.
4 - Atoms of one element cannot change into atoms of another. In a chemical reaction the atoms only change how they are bound together.
Cathode Ray Experiment
J.J. Thomson’s experiment
Applied a high electrical voltage between two electrodes. Discovered electrically changes particles for the first time. Declared the “Plum Pudding” atomic model.
Electrostatic Forces
fundamental property of some of the particles that compose an atom(Positive and Negative charges) that either attract or repulse forces.
Electric Field
The area around a charged particle where electrostatic forces exist.
Electron
J.J. Thomson
a negatively charged, low mass particle present within all atoms.
Millikan’s Oil Drop Experiment
Let oil drop by gravity through an electrically charged gas towards a negatively changes metal plate. The oil drops fall would slow, stop, or reverse depending on the strength of the charge.
Electron Charge
-1.60 X 10^-19 C(coulombs)
Fundamental charge of a single electron.
Charge to Mass ratio
-1.76 X 10^8 coulombs(C) / gram(g)
Radioactivity
Henri Becquerel and Marie Curie
The emission of small energetic particles from the core of certain unstable atoms.
Allowed researches to probe the structure of an atom.
Types of Radioactivity
Alpha(+ and most massive), Beta, and Gamma
Rutherfords Gold Foil Experiment
Ernest Rutherford.
Attempted to prove Thomsons “Plum Pudding” model but instead disproved it on accident.
Found alpha particles were deflected off of something in the middle of an electron cloud and therefore there was something holding electrons together at the center. Basis for the Nuclear Model(Nucleus in electron cloud contains Neutron and Protons)
Nuclear Theory
Ernest Rutherford.
- Most of the atoms mass and all of its positive charge are contained in a small core called the nucleus.
- Most of the volume of the atom is empty space, throughout which tiny, negatively charged electrons are dispersed.
- There are as many negatively charged electrons outside the nucleus as there are positively charged particles(protons) within the nucleus(atom is neutral)
Nucleus
Small core of an atom with most of the atoms mass and all of the positive charge. Contains both neutrons and protons and accounts for over 99% of the atoms mass.
Proton
positively charged particles within the nucleus
Neutrons
Neutral particles within the nucleus
Atomic Mass Unit(amu)
1/12 the mass of a carbon atom containing six protons and six neutrons.
1 Proton = 1 amu
1 Neutron = 1 amu
1 Electron = 0.00055amu
Atomic Number(Z)
The number of protons in an atoms nucleus.
Chemical Symbol
each element is defined by its unique atomic number and represented by a symbol.
Isotopes
Atoms with the same number of protons but differing numbers of neutrons.
Natural Abundance
The relative amount of each different isotope of an atom naturally occurring in a sample.
Mass Number(A)
the sum of an atoms protons + neutrons(isotopes chance the number slightly)
Ions
Atoms who has either lost of gained electrons giving them either a positive or negative charge.
Cation
Positively charged Ions.
Anion
Negatively charges Ions.
Periodic Law
Dmitri Mendeleev.
When the elements are arranged in order of increasing mass(not atmoic number like today), certain sets of properties recur periodically.
First periodic table.
Periodic Table
Classification of elements based on increasing atomic number and their properties.
Metals, nonmetals, and metalloids.
Metals
lower left side and middle of periodic table.
Good conductors of heat and electricity, malleable(into flat sheets), ductile(drawn into wires), often shiny, tend to lose electrons when they undergo chemical change.
Chromium, copper, strontium lead, etc.
Nonmetals
upper right corner of periodic table divided by a zig zag line towards bottom right from Boron to Astatine.
Varied properties. Generally poor conductors of heat and electricity and all tend to gain electrons when they undergo chemical change.
Oxygen, sulfur, carbon, bromine, iodine, etc.
Metalloids
Mixed properties of metals and nonmetals.
Many are semiconductors. Good for anything with computer chips.
silicon, arsenic, antimony etc
Semiconductor
Type of metalloid.
intermediate(highly temperature dependent) electrical conductivity. Very useful.
Main Group Elements
groups on the periodic table with properties which tend to be largely predictable based on their position on the table.
Have an “A” associated with the number.
Transition Elements(or Metals)
elements whose properties tend to be less predictable based simply on their position on the periodic table.
Have a “B” associated with the number.
Family(Group)
A column within a maingroup on the periodic table. Usually share similar properties.
Noble Gases
Group 8A.
Mostly unreactive(stable) elements.
Helium(He), Neon(Ne), Argon(Ar), Krypton(Kr), Xenon(Xe), etc.
Alkali Metals
Group 1A.
Reactive metals.
Tend to lose 1 electron and become a 1+ ion(cation).
Lithium(Li), potassium(K), rubidium(Rb), etc.
Alkaline Earth Metals
Group 2A.
Fairly reactive but less than Alkali Metals.
Tend to lose 2 electrons and become a 2+ ion(cation).
Calciums(Ca), Magnesium(Mg), Strontium(Sr), Barium(Ba), etc.
Halogens
Group 7A.
Very reactive nonmetals.
Tend to gain 1 electron to become a 1- ion(anion)
Chlorine(Cl), Bromine(Br), Iodine(I), Fluorine(F), etc
Ions and the periodic table
- A main-group metal tends to lose electrons, forming a cation with the same number of electrons as the nearest noble gas.
- A main-group nonmetal tends to gain electrons, forming an anion with the same number of electrons as the nearest noble gas.
Atomic Mass(Amu)
the average mass of the isotopes that compose an element weighted according to the natural abundance of each isotope.
Atomic Mass(Amu) = (fraction of isotope 1 * mass of isotope 1) + (Fraction of Isotope 2 * mass of isotope 2)… = X amu
Located directly beneath the symbol for the elements on the periodic table.
Mass Spectrometry
a technique that separates particles according to their mass.
Abundance of an Isotope = (100%/% Isotope 1 + %Isotope 1) * 100% = relative % to other ions of same element.
Mole(mol)
the amount of material containing 6.02214 * 10^23 particles.
The value of a mol is equal to the number of atoms in exactly 12 grams of pure carbon-12.
12g C = 1 mol C atoms = 6.02214 * 10^23 C Atoms.
Avogadro’s Number
Amedeo Avogadro.
6.02214 * 10^23(a mol)
Molar Mass
1 mol of atoms of an element.
An elements molar mass in grams per mole is numerically equal to the elements atomic mass units.
Conversion between mass and moles
Copper(Cu) has 63.55 amu and a molar mass of 63.55 g/mol.
63.55g Copper(Cu) = 1 mol of Copper(Cu) = 6.02214 * 10^23 Cu atoms.
Volume
V=4/3(pie)(r)^3
Diatomic
Have, No, Fear, Of, Ice, Cold, Beer
H2,N2,F2,O2,I2,Cl2,Br2
H,N,O and Group 7A are Diatomic
