Week 3 Flashcards
What do we know about electricity?
Scientists noted that if one passes electricity through colored solutions with wires, MASS was deposited and lost on the electrodes
Black wire - ANODE
Red wire - CATHODE
What do we know about ions ?
Accepting/ loosing electricity can be thought as an ATOMIC PIGGY BANK. The currency is the electron
IONS are matter which are CARRIERS OF ELECTRICITY
IONS which contain a NEGATIVE CHARGE ( extra e-) are attracted to the ANODE (electrode). A minus sign A- is used
Ions which are POSITIVELY CHARGED (less e-) are attracted to the CATHODE(electrode). A positive sign A+ is used
What are the experiments for electron transfer ?
Galvanic cell - spontaneous free electron transfer
Electrolytic cell - forced electron transfer
What is the cathode Ray tube
When scientists generated the ability to generate strong electronic current
Using materials that glow (FLUORESCENCE) , a beam of electrons is visible
This is called a CATHODE RAY TUBE- used in old TVs
A magnet (electronic field) will detect the electron beam. Hence electron has negative charge
How do we know how much negative charge does an electron hold?
From the MILLIKAN OIL DROP EXPERIMENT, we create negative (anions) ions with XRAYS
Using an EXTERNAL ELECTRIC PLATE, we balance the ions and record the value
The mass to charge ratio is 9.1 *10^-28g
How do we know that atoms have a nucleus ?
Particles generated from a radioactive source( ALPHA RADIATION) are projected at a super thin layer of gold foil
Detection screen around the foil flashes in contact with these particles
The particles were deflected back at all angles, why?
The, experiment RUTHERFORD wrote. Was the most incredible thing that happened to him, like fireing 15 inch shell at tissue paper and it bouncing back
Most particles pass through without hitting anything
Some particles hit something very big as indicted by particles bouncing back, this is the nucleus
What is the nucleus made of ?
Nucleus was found to be a relatively massive object
99% of atoms mass
Nucleus is composed of TWO types of particles:
The PROTON is positively charged +
The NEUTRON has NO CHARGE and is not attracted to other charged particles
Describe protons, neutrons and electrons
Proton and neutron make up atomic nucleus at the centre of the atom
The Nucleus is POSITIVELY CHARGED +
The rest of the space in the atom is occupied by electrons moving around the nucleus
Space which the electron occupies in an atom is incredibly vast
Proton-> 1.673 *10^-27
Charge = +1
Neutron - > 1.675 * 10^-27
Charge = 0
Electron -> 9.109* 10^-31
Charge = -1
Why are protons important for an element ?
The number of protons (z) defines an element
However the number of neutrons within a nucleus can be different
Thus different elements have different ISOTOPES, same no. of protons but different no. of neutron
Eg. Z= 1 hydrogen, deuterium(D) and tritium (T)
What is an isotope?
Isotopes are naturally occurring. But each isotope has a DIFFERENT MASS
Why? - different number of neutrons
Number of neutons + protons A
X
Number of protons Z
Eg. Chlorine is important since it kills bacteria
Here is common isotope of chlorine
35
CL number of neutrons = 35-17= 18
17
How do electrons behave within an atom?
Since electrons have a NEGATIVE charge they don’t like each other, they REPULSE or avoid each other
Electrons need to be on separate tracks to avoid collisions, we call these tracks ORBITALS
A group of ORBITALS is called a SHELL
Describe electrons and shells
There are limits to the number of electrons in a shell. You must learn the pattern for the first 2 rows of elements
Hydrogen 1st shell 1e-
Helium 1st shell 2e-
Lithium 2nd shell 1e-
Neon 2nd shell 8e-
What are the balance and core shells ?
The maximum is 8 electrons in a shell
Once second shell is filled we go to the 3rd and so on
Sodium -> 3rd shell 1e-
We call the outer shell - VALENCE
We call the inner shell - CORE
