Unit 2 Notes Flashcards
Why do we use atomic mass units (amu)?
It is used to express the relative masses of atoms and subatomic particles. It would be really hard to measure a single atom in grams.
What are isotopes?
Atoms of an element containing different numbers of neutrons?
Do the number of protons change with different isotopes?
No
What is Avogadro’s number?
6.022 x 10^23 particles/mole
What is molar mass?
Mass in grams of one mole of a substance
The (blank) determines on element from another. In other words the # of (blank) determines one element from another.
Atomic #
Protons
In determining molecular mass, we multiply the experimentally determined masses of each isotope by their
% natural abundance
How do isotopes differ?
of neutrons
What are the 3 different isotopes of hydrogen?
Hydrogen/protium h,1,1
Deuterium h,2,1
Tritium h,3,1
How do you calculate the average atomic mass of an element?
Atomic mass x percent abundance + atomic mass x percent abundance
Kinetic molecular theory relates to what?
The drawing of solids, liquids, and gasses and the particles
All matter consists of (blank)
Atoms
Who discovered electrons using a cathode-Ray tube
JJ Thomson
Who was not sure where electrons fit into the structure of atoms?
JJ Thomson
Streams of electrons emitted by the cathode in a partially evacuated tube
Cathode rays
Subatomic particle that has a negative charge and essentially zero mass
Electrons
Who calculated the mass of the electron?
Robert Milikan
Who created the plum pudding model?
JJ Thomson
Who discovered radiation from Uranium?
Henri Becquerel
Who showed radiation containing particles and rays?
Curie and Rutherford
Spontaneous emissions of high energy radiation and particles by materials
Radioactivity
Who calculated the mass to charge ratios?
Rutherford
A radioactive emission that is a high energy electron
Beta particle
A radioactive emission with a charge of Z+ and a mass equivalent to that of a helium nucleus
Alpha particle
What did Geiger and Marsden do?
Tested the plum pudding model - discovered + charged nucleus where most of the mass of the atom is held
The positively charged center of an atom that contains nearly all the atoms mass
Nucleus
A positively charged subatomic particle present in the nucleus of an atom
Proton
An electronically neutral subatomic particle found in the nucleus of the atom
Neutron
Who discovered and characterized free neutrons to make the model of the atom complete?
James Chadwick
Unit used to express the relative masses of atoms and subatomic particles
Atomic mass unit (amu)
A unit of mass identical to 1 atomic mass unit
Daltons
Who published the 1st table of atomic masses?
John dalton
Who built modified cathode ray tubes that were evacuated except for small quantities of fill gases?
Francis W Aston
An atom or group of atoms that has a net positive or negative charge
Ion
Atoms of an element containing different numbers of neutrons
Isotopes
The nucleus of a specific isotope of an element
Nuclide
The # of protons in a nucleus of an atom
Atomic # (Z)
Either a proton or a neutron in a nucleus
Nucleon
The number of nucleons (proton plus neutron) in an atom
Mass number
Chart of the elements in order of their atomic #s and in a pattern based on their physical and chemical properties
Periodic table of elements
Who- Theory of chemical atomism- matter is composed of atoms and atoms are indivisible and indestructible
John Dalton
Discovered radioactivity and isolated the previously unknown elements polonium and radium
Marie curie
Proved that atoms are made up of smaller particles
Marie curie
Spontaneous emission of energy and particles from atomic nuclei
Radioactivity
For neutral atoms, the number of what equals the number of what
Protons = electrons
Defined as exactly 1/2 the mass of a carbon-12 atom
1 amu
“Electrons are distributed through a uniformly charged (+) sphere of atomic dimensions
JJ Thomson
Describe the plum pudding model
Electrons are like raisins dispersed in a (+) charged pudding could
Who determined the charge to mass ratio of an electron
JJ Thomson
Who performed experiments involving charged oil drops and determined the mass of the electron?
Robert Andrews Milikan
Who tested Thomsons pp model? How?
Rutherford
Directed alpha particles at metal foil pieces and found that some deflected back at high angles- discovered nucleus
Who created the “nuclear model”
Rutherford
Atom is a dense center of positive charge surrounded by electrons
Nuclear model
All atoms of an element have the same number of what?
Protons
The # of protons in the nucleus
Atomic #
Tells us the mass of one atom of an element RELATIVE to one atom of another element
Atomic weight
A weighted average of masses of all isotopes of an element, calculated by multiplying the natural abundance of each isotope by its mass in atomic mass units and then summing the products
Average atomic mass
The proportion of a particular isotope, usually expressed as a percent, relative to all the isotopes of that element In a natural sample
Natural abundance
Equation for average atomic mass
Mass of each isotope x natural abundance and then sum the weighted masses
Who showed that subjecting a mixture of gasses present in earths early atmosphere to an electric current could produce amino acids
Harold Urey and Stanley Miller
A substance consumed during a chemical reaction
Reactant
A substance formed during a chemical reaction
Product
What do chemical equations describe?
Reactions
A reaction in which two (or more) substances combine to form one product
Combination reaction
An amount of material that contains Avogadro’s number of particles
Mole
The # of carbon atoms in exactly 12 grams of the carbon 12 isotope
Avogadro’s number
The mass of 1 mole of a substance
Molar mass
Sum of protons + neutrons for an atom
Mass number
Atoms of the same element but different mass number
Isotopes
Number of atoms of a given isotope divided by total number of all atoms of all isotopes of the element x 100
Percent abundance
Experimentally determined mass of an atom of one isotope
Exact mass of isotope
Determination of masses of isotopes
Weighted average of atoms in a natural sample of element
Mass spectrometer
One mole always contains the same (blank), no matter the substance
Number of particles
Avogadro’s number
6.022 x 10^23 particles
Mass in grams of one mole of a substance
Molar mass
Who created the first periodic table?
Dmitri Mendeleev
How did Mendeleev arrange elements?
Based on similar chemical properties and increasing atomic mass
