Chapter 2 Flashcards
Law of conservation of mass
In a chemical reaction, matter is neither created or destroyed
○ Ex: reaction between sodium and chlorine to form sodium chloride. The combined mass of reactants sodium and chlorine exactly equals the mass of the product sodium chloride
What is the law of definite proportions
all samples of a compound, regardless of where they’re from or how they’re prepared, have the same proportion of constituent elements
What is the law of multiple proportions
When two elements (A and B) form two different compounds , the masses of element B that combine with one gram of element A can be expresses as a ratio of small whole numbers
Difference between law of definite proportions and multiple proportions?
? The law of definite proportions applies to two or more samples of the same compound and states that the ratio of one element to the other is always the same. The law of multiple proportions applied to two different compounds containing the same two elements A and B
What laws led to the modern atomic theory
law of conservation of mass, law of constant composition, and the law of multiple proportions
Elements are composed of ____ ______ called ____
tiny particle, atoms
All atoms of a given_____ have the same identical_____ that are different from other_____
element, properties, elements
_______are formed when____ of different_____ combine in simple_____ _____
Compounds, atoms, simple numerical ratios
A chemical reaction only involves _____, _____, or ______ of atoms. Atoms can’t be ____or _____ by chemical techniques
combination, separation, rearrangement, destroyed, created
JJ Thomson proposed what model for the atom
The plum-pudding model, negatively charged electrons are small particles held in a positively charged sphere
What was Rutherford’s gold foil experiment?
Performed to confirm the plum-pudding model. Directed positively charged “alpha” particles at an ultra thin sheet of gold foil. If gold atoms were like the plum-pudding model, the particles should pass through gold foil with minimum deflection.
What happened in Rutherford’s gold foil experiment?
Some of them bounced back, suggesting a small dense nucleus. Rutherford thought that matter in a atom must not be uniform
Conclusions from Rutherford’s experiment
Still hold up today:
- Most of the mass of the atom is concentrated in a positively charged center, the nucleus. Around the nucleus, the negatively charged electrons move
- There are as many negatively charged electrons as there are positively charged protons
- Most of the mass of the atom is concentrated in the nucleus which occupies a small portion of the volume(space) of the atom
What is 1 amu
defined as 1/12 the mass of a carbon atom that has 6 protons and 6 neutrons
What letter represents the atomic number?
Z
What does the atomic number represent?
the number of protons in the nucleus of the atom
What letter represents the Mass number?
A
What does the Mass number represent?
the sum of the number of protons and neutrons in the atom
What is the similarity and difference between protons and electrons?
They are almost equal in magnitude (similarity) but opposite charge (difference)
What is an isotope?
Atoms with the same number of protons but different number of neutrons
What defines an element?
The number of protons
What is atomic mass?
average mass for each isotope of an element
-atoms of an element can have different masses because of isotopes so atomic mass is an average
How to calculate atomic mass?
fraction of isotope1massofisotope1+fractionofisotope2massifisotope2
What is natural abundance?
percentage of isotope in nature
Mass Spectrometry is a technique that does what?
separates particles according to their mass
What is measured using mass spectrometry?
mass of atoms and the percent abundances of isotopes
What is the result of mass spectrometry?
A graph called mass spectrum, looks like a bar graph
What does the position of peak on x axis tell us?
the mass of the isotope
What does the height of peak tell us?
the height is called intensity and its value is the relative abundance of the isotope
