3.1 - Electron Theory - 3q Flashcards
What does the term matter mean?
Matter is anything that has weight and occupies space
How many elements have been idenified and how many of these occur in nature?
There are 118 elements that have been identified
Of these, only 94 occur in nature, these are called the natural elements
In terms of electron theory, what is the weight and location of each sub atomic particle?
Nuetrons and protons have approximately the same weight and size
They are much heavier than electrons meaning the weight of an atom is determined primarily by the number of protons and neutrons in the nucleus.
What is special about the Hydrogen atom?
One electron orbiting one proton
Contains no neutrons
What is meant by an atom that is in its normal balanced or neutral state
The electrons are equal to the number of protons
What is Ionization
Ionization is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form an ion
Why does an electron keep orbiting a nuclues and not fly off?
The centrifugal force of the electron that thrusts it away from the nuclues is exactly offset by the attraction of the protons in the nucleus.
What is the name given to the outermost shell of an atom?
The outer shell is called the valence shell and the electrons in this shell are called valence electrons
What are inert gases?
Inert gases have 8 electrons in their valence shell. The valence shell is completely filled and as a result these elements are so stable that they resist any sort of chemical activity. They will not even combine with other elements to form compounds. They are also reluctant to give up any electrons.
Examples: Neon, Argon, Krypton, Xenon, Radon
What are two materials that are semiconductors?
4 electrons (shell half full)
Germanium
Silicon
What is the definition of matter?
Matter describes everything that has weight and occupies space.
Name the components of an atom?
Electron, proton and neutron (except Hydrogen)
What is the only element that does not contain a neutron?
Hydrogen
Which is the lightest sub-atomic particles
Electron
What is the most complez element found in nature?
Uranium
92 electrons, 92 protons
146 neutrons
An atom is electrically neutral. What does this mean in terms of its sub-atomic particles?
The number of protons in the atom is equal to the number of electrons in it
What is an Ion
An ion is an atom that is positively or negatively charged i.e not in its natural state
How is a negative Ion formed
Surplus of electrons
What can cause atoms to loose electrons
The outermost electrons (valence electrons) are loosely bound to the nucleus. Hence, these electrons keep moving from one atom to another (direction of current)
Which electrons are easily freed and used for electrical conduction?
Electrons in the outermost shell (valence shell)
An element whose valence shell is filled is called what?
Insulator
How do you categorise the following amount of electrons in the outermost shell>
1 - 3
4
5-8
1 - 3 = Conductor
4 = Semiconductor
5 - 8 = Insulator
A substance with a large number of free electrons is called what?
Conductors
What is a compound?
A compound is composed of two or more elements
Define the following:
Atomic Number
Atomic Weight
Atomic number is the number of protons in the nucleus of an atom
Atomic weight - total mass/weigth of an atom
Give three examples of conductor, insulator and semiconductor
Conductor: Tungsten, Aluminium, Gold, Copper, Silver
Semiconductor: Germanium, Silicon
Insulator: Teflon, Fused Quartz, Wood (dry), air, hand rubber, glass, plastic and paper (dry)
Define Ionization
Ionization is the process by which an ato or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions
