ATOMIC THEORY Flashcards
Who discovered that atoms were the smallest indivisible particles of an element
John Dalton (18th century)
What was the limitation of dalton’s atomic theory
He did not explain the existence of isotopes
What were the postulates in dalton’s atomic theory
- Atoms are the smallest indivisible particle of an element
- Atoms of the same elements are alike in every aspect but differ from that of other elements
- Every chemical reaction is as a result of the combination or separation of atoms
- Atoms combine in small amounts/quantities to produce molecules
State the law of definite proportion and give another name for it
All pure samples of a compound contains similar elements in the same proportion by mass (Law of constant composition)
State the law of multiple proportion
When two elements A and B combine to form more than one compound, then the various masses of element A that combines with a fixed mass of element B are in simple ratio to one another
What are isotopes
Isotopes are atoms of the same element that have the same number of protons and electrons but different number of neutrons
Why does dalton’s atomic THEORY still hold inspite of isotopes
The discovery of isotopes would mean that atoms of the same element would have different masses, but since isotopes are present in fixed proportions, the average mass of atoms is still constant and the theory still holds
What happens when the neutron number of an isotope is too high
The nucleus becomes unstable and the element becomes radioactive
Who created the mass spectrometer
Aston (1919)
What is used to measure the atomic masses of elements
Mass spectometer
What are the five stages involved in measuring atomic mass using a mass spectrometer
- The atoms is vaporized
- +ve ions are discharged
- +ve ions are accelerated by electric field
- the ions are deflected by a magnetic field
- ## the ions are detected on reaching the detector and record is made
How are the +ve ions in the mass spectrometer created
They are created by bombarding neutral atom with high energy electrons
What is mole
Mole is the amount of a substance that contains as many particles(6.02 × 10²³) as are in 12g of carbon-12
How are the elements in the periodic table arranged
Thay are arranged in order of increasing atomic number
What is excitation
This is when an electron moves from lower energy level to a higher energy level
What happens when an electron is exited
It becomes unstable and gives out the excess energy in form of radiation which produces a spectrum
What is ionization energy
Ionization energy is the amount of energy required to remove an electron from a gaseous atom in its ground state
Why is the ionization energy of noble gases high
They are stable
What branch of chemistry deals with the weight relations between elements and compound in a chemical equation
Stoichometry
What are the shapes of the s and p orbital
S orbital - spherical
P orbital - dumbbell
Where is the nucleus located in the p orbital
Below the two halves of the dumb bell
State Boyle’s law
Boyle’s law(1662) states that the volume of a fixed mass of gas is inversely proportional to its pressure at constant temperature
At what pressure is Boyle’s law properly obeyed
At or below 1 atm
What are the types of cohesive forces
Electovalent /ionic
Covalent
Metallic
Vanderwaal
Mention some phenomena that support kinetic theory
Brownian motion
Osmosis
Diffusion
What are the assumptions of kinetic theory
- Gas particles are in constant rand motion in a straight line
- Their collisions are perfectly elastic
- Their collisions with the walls of the container results in pressure
- The volume fo gases are negligible when compared to the volume occupied
- The cohesive forces between gas particles are negligible
- Tbe temperature is a measure of the average kinetic energy of the particles
State Charles’s law
At constant pressure, the volume of a given mass of gas is directly proportional to the temperature
State dalton’s law of partial pressure
(1802)It states that when there is a mixture of gases which do not react chemically together, the total pressure of the system is the sum of the partial pressures of the individual elements
State Graham’s law of diffusion
(1833) It states that the rate of diffusion of a gas is inversely proportional to the square root of its density
What is the critical temperature of a gas
It is the temperature above which a gas cannot be liquefied by pressure
What is the critical pressure of a gas
It is the pressure at which the critical temperature is just enough to liquify the gas
Mention some applications of Graham’s law
- it’s used to separate mixed gases(atmolysis)
- It’s used to determine density of gases
State gay-lussac’s law of combining volumes
It states that when gases react, they do so in volumes which are simple ratios to one another and to the volumes of their products if gaseous provided that the temperature and pressure are kept constant
State avogadro’s hypothesis
It sates that equal volume of all the gases at the same temperature and pressure contain the same number of molecules
When do avogadro and Gay-lusaac laws hold
At low pressures
Root mean square velocity
(3RT/m(in kg/mol))½
